So I've been looking into changing over to Speedplay's as an upgrade from my Shimano SPD M520's

From the descriptions on the Speedplay site it doesn't seem as if there's that much of a difference between the X's and the Zero's other than about $15 between the two for the Chrom-Moly version. They both seem to have float adjustments. Zero's seem to offer a tad bit more adjust ability. I'm assuming I should rule out the light action if I'm contemplating getting it some racing next year.

Overall it looks like any of those models are not compatible w/ on another.

A quick searching on the topic I see many people use the Zero's. Although I'm not sure between the X's or the Zero's what's the better choice as the Price difference isn't really an issue.

Any input would be greatly appreciated.

X's have no float adjustment. They have unlimited non-centering float. I've used them and liked them for years. Never tried the Zeros

As cranky said, X-series has no float adjustment. The zeros have limit screws so that you can set how much float, if any, that you want. I like the pedals but I don't like the float, I have them cranked down to zero.

Love my X5's. So easy to get in and out, yet I've never came out accidentally. I also don't find the cleats difficult to set-up, as some would have you believe. Read the manual.

Zeros. You can use the float limit set-screws to adjust your foot position right where you need it. Proper setup is important. Yes, RTFM.

Zeros also have an improved spring design that do not foul with dirt as easily as the exposed wires on the X-series cleats. Note that the "light actions" use the same basic spring design and are cross-compatible with zeros despite the official line that they are not compatible. If you want the new spring design but want it to be easier to get into and don't care about the adjustment, light actions are a good way to go.

+1

personally, I'm surprised speedplay still offers their older X series pedals when the zero and light action fill the role.

I have been on the Light Action pedals for four years and I think there are great. If I raced, I would probably go with Zeros. I don't see any reason to go with the X series unless you already have a pair. It is my understanding that it takes about twice as much pressure to go engage the cleat spring on the Zeros as it does the Light Action pedals.

I use x/2's mostly for legacy reasons. On a clean slate, I'd go with zeros. Also I'd avoid thee cro mo ones either x or zeros due to rust issues.

Well it looks like I'll be looking into Zero's and I didn't think about rust issues w/ Crom-mo but I don't see it being a huge issue I always store my bike in the basement, and when I clean it I've very meticulous, but I'll keep it in mind when I do decide to buy them.

Perhaps not an issue in Conn. However in a coastal environment, humidity and salt air can create a rust issue with the cro mo, sufficient justify a fe bucks more for stainless steel.

I typically don't ride in the rain, but thought long and hard about the stainless Speedplays when I built up my BMC. I couldn't really find a justification for anything other than the CroMoly, but damn the 20g saving of the titanium would be nice

Between the Zeros and the X's, unless you know you like a ton of float (15 degrees is a lot), go with the Zeros. Wide open, the Zeros are like being on ice skates when you first start. Because of my knee issues, I like having the float, but over time have dialed it down to just a few degrees. The Zeros also allow you to create a more toe in (or heel) or toe out position depending on your body.

Stainless Zeros.

I like the cromoly pedals because I can attach my speed sensor magnet to one of the pedals. So far I haven't had an issue with rust, but the paint has worn off part of the spindles.