I've got lots of experience with the Compact. I own two (although one stopped beeping after changing the batteries...grrr!). I bought them because I absolutely HATE the yellow color on the big watch. They've always been wonderful for me, but I don't have any comparison. The screen and buttons ARE smaller, but since I use fingerless gloves on XC, pressing the button out of the start box is just fine. I also don't really look at the screen, I just know where my minute marks are and can tell by the beeping of my watch every minute how on or off we are.
Having said that, they have the same battery issue as the yellow one. Also, even though it's compact, it's still a bit too large for me to wear around all day. I have pretty small wrists though.
Through prelim, I find I am fine with just my regular watch (Timex Ironman). Buttons are easy to reach, numbers easy to see and that way, since I am already wearing it, I have one less piece of equipment to worry about (always good)
I am not a spring chicken any more and neither are my eyes.
I like the big yellow one since I can actually SEE the numbers. Without having to look-look and focus hard on it. I can glance at it and the numbers are big enough that any fuzziness is not an issue.
I have both -- the compact one stopped beeping when I changed the batteries, so it has been relegated to conditioning days (when I find it easy just to look and see rather than hear, but I am wearing it all day at the barn so the small size is comfy).
Around the time it stopped beeping I literally discovered a yellow one buried in a pile of saddle pads in my trailer -- I was cleaning out the dressing room and there it was. I have never purchased one, so this one was obviously "left" by someone who hitched a ride...but since no one I ride with is missing one, and no one ever claimed it...
I started competing in it, and I do like it a bit better for actual competitions...although it is SO big it is possible for me to accidentally hit one of the buttons just by bending my hand...
so I would vote for compact, unless you need the extra size visually.