It's the pedals themselves. I have two bikes, both with SPD pedals, but different ones. The nice road bike has a set of A-520s I got from the store. The commuter/errands/rain bike has something like m-520s, I'm not sure which, that I got used and cheap. I've unclipped accidentally a bunch of times with that bike, with the pedals set to max release tension, but never from the nice bike with the A-520s. The other pedals are just old, and maybe crappy to begin with, I don't know, but I'm going to replace them soon.

I have them, but don't bother with them for Speedplays. They were pretty necessary for Keos, though.

OK, I race MTB, CX and Road.

My experience and my experience only as everyone turns the cranks a little different....

If you aren't accidentally unclipping during MTB and CX use, it is not going to be an issue on the road. Road racing (even a flat out sprint) is pretty tame compared to CX.

never saw the point of cleat covers...if I were planning on doing any amount of substantial walking, I would get spds/mtn bike shoes. cleats are fine for walking a few blocks (I've had to walk over a mile to fix a flat...didn't have any problems).

I've pulled out of them many times, and I've never used the multi-release cleat. I also run the pedal retention at maximum and have complained twice to the Shimano rep that they simply don't go high enough anymore. If I were going to pick out an SPD pedal from my arsenal for road sprinting, it would be my venerable M747s, which have considerably better retention than any current-gen model including XTR.

On the original topic, one of the strengths of true road pedals (besides the extra 1200 watts) is that they're designed for high cornering clearance. With my Speedplays, the shoe would hit the ground before the pedal did. Those A600s don't look too bad in that regard, so if you're going to race with SPD, that's probably your best bet. Replace your cleats every 6 months or so, to minimize risk of a pullout when sprinting.

I ride speedplay lite action's/ love em/ never had an accidental release. I do carry cleat covers with me on my rides just in case I cant fix something on the road and I need to walk home shamefully.

All this plus the contact area is much smaller than other pedals which means more difficult to transmit power, epsecially on all out efforts when you're tired and it does lead to discomfort, even with very stiff soles.

I don't understand why people keep trying to defned spd's for racing - it's something they aren't designed to do. I have both spd-sl (plus lots of experience with Looks) and spd. Each is good for their own purpose.

I notice the extra comfort and security of my road pedals. It's not a huge difference, but I'd have to be on a pretty tight budget not to want them on my road bike.

If you are on a tight budget though, don't worry about it. The spds will work fine.

I've been riding with SPD pedals on my road bikes from the beginning and have never had issues with them. I don't know what problems others have encountered on long rides, but I have ridden centuries with no problems. SPD pedals are fine on road bikes.

Not really an issue but there are couple of things I noticed could be better. 1) The stability of platform. Even with S-works MTB shoes (VERY STIFF), It's not quite as flat as road shoes when stomping on it. 2) limitation on float. I am in process of trying road pedal systems with much cheaper shoes right now (less stiff) but I can see how I would have much less hot foot issues, better stability at cost of walk-ability... and possibly easiness of clip in.
Besides, I noticed that my knee might like Speedplay better after some testing... going to give it few more days to see if it warrants dropping my over $700 worth of SPD stuff I have accumulated over time...

See though, here's the thing: you should never ever ever unclip accidentally in a sprint. It's a good way to give your dentist a large portion of several future paychecks.

Mtb pedals are made, in part, to unclip easily. Road pedals are meant to keep you fastened to your pedal full stop. It's like a ski binding in that way. Yes, you can get out of it, both routinely and if you crash, but its real job is to keep the skies firmly attached to your feet. This is why roadies prefer road pedals.

That said, if this is the OPs first time in clipless, Mtb pedals are the way to go. Easier to use and easier to get used to. But if you road bike for long enough, you will find yourself going for road shoes and road pedals. I recommend SPD-SL.

I think if you race long enough, you'll find you need 'road' pedals. Otherwise, for the majority of road cyclists, MTB pedals are adequate and, in many cases, superior.

Officer I surrender!! Merely stating pros and cons of different pedal types is all, Officer. Didn't claim anyone needed nothing, Officer. Can I go home now?

Wasn't I pretty much agreeing with you?

You tell me. You do seem to have a hangup on racers offering the "common folk" advice. I found the advantages and transitioned to "road" pedals years before I started racing.

Ok, I was pretty much agreeing with you.

I find that to be a rather strange accusation and I'm not sure where it comes from. Do I owe you an apology for something I wrote in another thread?

No doubt.

doubt it
wle