I have spoken to a couple of LBS about it but got nothing more than suggestions to change the pads or upgrade to dura ace callipers. Not exactly rocket surgery. The new pads have so far not been a great investment and I'm far from convinced that upgrading to dura ace or any other alternative callipers would change much at all.
As for the OP's question - I go back and forth from road calipers (Dura Ace 7900 and 105 5700) and Mini-V Brakes on a regular basis since my winter/rain bike has TRP CX9 Mini Vs. The CX9 mini-v absolutely unquestionably have more mechanical advantage than the caliper brakes, as there is always a few stops during the switch where I have to re-learn the amount of force required for a given amount of braking. However, as many have mentioned, the modulation is not as good. In the winter, when it's wet ALWAYS here, that doesn't really matter as the huge drop-off in pad-rim friction means I need more power for a given situation and that reasonably balances the modulation issue.
The main issue in the wet is the near total lack of stopping power (with any rim brake) that you can experience in the first moments of a braking effort. That's a problem for panic/emergency stops. I notice that the braking power ramps up as the rim gets swept dry. I think the most effective way to use rim brakes in the wet is to be proactive about 'wiping' the rims dry - periodically applying light pressure to clear off the rims so they are more ready when you need them.
If you're truly concerned with wet braking performance, you'll never be truly happy until you go to a front disc and caliper, as the real problem with wet braking is always going to be the pad-rim interface.
The OP's experience doesn't mesh with the majority of others' experiences.
If you can't lock a rear tire on dry pavement or flip over the bars if it's a front brake then something is dramatically wrong. Flex is an issue with cantilevers - just squeeze brakes on a showroom floor and watch the stays bow out - but such flex only comes into play at a force much higher than necessary to lock a tire in the dry at 10 mph.
I switched from Textro cantilevers to TRP CX8.4 on my commuter because I have to go down two steep grades on my way to work and I hated the lack of feel/power on the cantilevers.
If you have a bike equipped with canti-s, in my mind, switching to TRP CX series is a no brainer. Although they recommend to use the CX9 with Shimano Ultegra/Dura-Ace levers, I went with the CX8.4 since they have a bit less mechanical advantage and hence more modulation. You can call TRP and talk to them about what's right for you. And really, don't listen to some of the people on this thread that are basing their opinions on a bike ride they did in the 1950s ;-)
So, in summary, TRP CX8.4 is equal for me the the brakes on my Roubaix SL2. TRP CX.9 has more power but less modulation. If you are riding in the wet, I would use Kool Stop Salmon or dual compound pads.
Also try all-weather pads like koolstop salmons
What sort of surface treatment do your rims have? Some rims are hard-anodized a contemporary color (black) but don't have machined brake tracks to go with that so braking is inefficient until you wear through the coating.
My wife and I once bought matching "comfort" bikes which had "brake modulator" spring assemblies in the front cable which made it impossible for inexperienced riders to send themselves over the handlebars and the rest of us to stop on steep hills. In a sane world no manufacturer would be that stupid, although our world is litigious not sane.
I have calipers on my other road bike. This road bike was built on a cyclocross frame. Same wheelset though.
No rim treatment, just aluminium. The rest of the rims are annodized black but the braking surface is machined flat with two wear-indicator groves. I've scrubbed it good and proper with strong detergent, rinsed with fresh water, then rubbed with alcohol. I've also checked brifters and cables.
I've made some improvements by angling my brifters a little further down and preloading the levers slightly, but the difference is again marginal and the clearance I now have for wheels coming out of true on a ride is less than I'd like.
I only read a few messages here so I don't know if this was mentioned. I know you can replace cables and housing but there's one detail. You may have to replace the noodles as well. One trick I read here, you can take out the plastic thing inside the noodle, pass the cable through the noodle then slip on the plastic thing over the cable. That way you won't ruin the plastic thing inside when you pass the cable through the noodle. I mean you can push your cable against that piece of plastic to push it out before inserting the cable inside the noodle.
check the cables and housing. make sure everything is seated correctly. if you pull on the brake housing, with the lever in its resting position (ie not squeezed), there should be no play. also, what is the distance from the brake pads to the rim?
pics please, pics.
pics of the rims surface, brake pad surface, brake pad to rim distance, and length/routing of housing. also, i assume the cable is clamped down tight in the caliper?
as others have stated, something isnt right about your claim.
I can lock my calipers*, canti-levers, v-brakes, and disc brakes. For modulation though, disc rules (even on 23c tires).
*This is on old 1055 series 105 calipers from the 90s, 6600 ultegras, and tektros.
There's something wrong with your setup if you can't lock them up.
I weigh about 78 kg. Now I will admit that you are a decent amount bigger then me. That being said as others have been discussing it sounds more like some type of set-up problem. I would venture to ask this: Are your brakes and levers matched? I know that Shimano changed the pull ratio of them when they went to hidden routing, I also have experienced a very weird braking profile when I used SRAM levers with other Shimano calipers (Those felt more like using a V brake, braking was more difficult to modulate and had a very sudden, jerky, stop)
Another thing is that while people mention it: contaminated housing? When you say you get to the point of your hands hurting when you squeeze the brakes have you squeezed the levers all the way to the bars at that point? If not then definitely try replacing cables and housing. One thing I have seen on bikes where water is able to get trapped in a housing line is that the cable rusts and ends up making the whole system feel horrible. The other thing that could happen is that you could have a non-seated ferrule. If the end-point of your housing isn't seated against the shifter then you will definitely get crap braking performance.
All modern caliper brakes have the potential to send you over the bars. I'm betting operator error. Squeeze the **** out of those levers. In the rain, squeeze twice, once to clear water from the braking surface and again to modulate speed.
Ok, today I rode two other bikes back to back with mine, both recent trek madones, one complete ultegra and one complete dura ace and both very well serviced. There was some (small) difference in brake feel but no difference in braking power (this was in the dry). Whilst I was there I tried my dad's old trek cromoly fixed fork mtb with early V-brakes and this braked far better than any of the road bikes - both better feel and lower effort at the bar for equal stopping power - easy to endo and still not go over the bars. Tempting to think that this could be due to a larger contact patch but with all four bikes the limit of deceleration (this was dry) was the need to avoid going over the bars, not the need to stop the wheel locking.
Me and my old man then serviced my brakes, cleaning and re-greasing cables (replacing front brake cable) and checking setup carefully. I'm now completely happy that the rims, pads, cables, cross lever, ferules/receivers, brifter, bar and settings thereof are as perfectly clean/lubed, adjusted and positioned as they can be. This yielded a slightly slicker brake feel, but no difference in braking performance that I could tell. It also closed the gap with the madones such that there was no longer any difference in the dry that I could tell, neither in feel nor power. I'll have to wait until I get a properly wet day again to check wet performance but I'm doubtful there'll be any difference.
I'm fast approaching the conclusion that calliper brakes (at least the sora-105, ultegra-ultegra and d.a.-d.a. brifter-calliper combinations that I've used) simply don't have the mechanical advantage to meet my personal expectations - at my weight - of braking performance in the wet.
Given that I know that mini-Vs have significantly greater mechanical advantage over callipers I'm tempted to think that this may be an option, but I also expect that a higher advantage with the same cable pull is likely to result in a on-off feel. I wouldn't want to upgrade fork and brakes only to have to do so again.
So, I'm also approaching the conclusion that if you're heavy, regularly ride fast in foul weather and want to know that you have plenty of power and modulation on tap regardless then discs might be the only way to go.
Thanks for your input folks, I will update again when it rains!
PS: This is Wales, so probably soon.