Originally Posted by Andrew R Stewart

To answer your question best I can- I suspect the caliper that has the longer arms to the cable anchor and casing stop will have the greater "power". This assumes that the other lever arms in play (and that's all non cammed systems are WRT the base mechanics), the two both have the pads positioned in the slots to contact the rim and the location of the arm pivots relative to all this would be the same. For a single pivot caliper there's only one pivot and it's distance from the rim brake track center is the same for both sides/pads/arms. Thus with a single pivot caliper the one with the longer cable acting arms are the greater the leverage. But with two different dual pivot calipers the dimensional assumptions can cause real life being different as all the real lever lengths are measured and compared. I'll also say that rider perception is not always in agreement with the measured numbers.

As far as pads not opening enough for wide tires goes- On my 32 and narrower tired road bikes I run Shimano R600 calipers with their QR and Ergo levers with that QR too. On my touring rig, the tandem and the Mongoose Tomac MtB I have cantis, thank you. In all seriousness consider wider rims the next time around as the QR range starts only after the brake is adjuster properly and the wide tire and narrow rim combo will exceed this most every time (or for the calipers designed when 23/25 wide tires were the cat's meow, note I don't say when sold...). Of course the annoying solution is to deflate the tires and/or use your hand as a hammer and hope the pads stay put. Andy