Hello, everyone!

I've really enjoyed browsing the forums -- it's got me psyched about trying off-road cycling. I'm an ultrarunner who would like to get into xterras, especially since I'm used to swimming in open water and most ultras are on trails.

However, I'd like to purchase a bike that I can also use for commuting, and possibly road races.

So, my question: would it be better to go with a hybrid or a cyclocross? Would the 'cross be more efficient, but maybe not handle well on technical trail? Also (sorry for the many questions), I am 5'1" and worry about finding something that will fit me well. Are there certain manufacturers you would recommend?

Thanks so much!