I'll weigh in.

If you're racing, find out if there is neutral support at your local races. If so, find out what they offer. One of our local series only has 9-speed wheels, so if you're running 10-speed you'll need your own support.

I started out with Shimano 9 speed on my cross bikes (there wasn't Shimano 10 speed at that time). I run Campy 10 speed on my road bikes. Over the years, I realized I had way too many duplicates of things that weren't interchangeable (namely, wheels and cassettes). So I eventually transitioned my cross bikes to Campy 10 as well. And I wouldn't have it any other way now. Not to mention all the shifting confusion created when switching almost daily between Shimano and Campy.

One advantage of running Shimano 9 speed is that you can run a mountain bike rear derailleur and a 34 cassette so you get fabulous climbing gear. Although your races may not be too hilly, you may want to do some trail riding on your cross bike and I found the extra gearing really helped me. With Shimano 10-speed, you can only go up to a 27 in the rear. With Campy 10-speed you can go up to a 29 in the rear.

Much of your decision will depend on your fitness and the terrain you plan to ride.

The other decision is what to run in the front. I run a compact crank with a 48-34. I can also switch this to a 50-34 if I plan to do lots of road riding on my cross bike. I typically don't run the 50-34 during the race season because of the additional chain slack. Some racers just run one chainring in the front.

In CA, we have a variety of courses and at least one every year has a hill that just kicks your butt! I found the 34 extremely useful, especially in seasons when my climbing wasn't as good.

Hope this helps!