For true XC racing, the smaller the CamelBak, the better. Yes, you need a pump, tube and a multi-tool, but in a race situation, that is likely all you need to carry in the actual pack. I have a small 50 oz that I carry when I race, and it can hold those items nicely. My food goes in the leg of my shorts for easy access.

I've done races with a saddle bag and water bottles, but don't drink enough with just the bottles. And in the races here, at least, the courses are multi-lap. So, if you have a REAL problem, you are never too far from help.

SheFly