Blood Bowl is one of the best GW games ever released. It is fun, random and a lot quicker then a game of fantasy. Cheaper as well. Easier to learn.
Oh, there's thousands of upsides to the game.
On to your question;
All the "hard" races are pretty much the same in Blood Bowl as they are in Fantasy. The elves, humans and so on are slightly different though. They
can be good at all parts of the game, whereas the orcs and chaos can only really run with the ball, preferably through their opponant.
Its pretty hard to describe the strenghs and weaknesses of every team (for one thing there are far more teams then there are armies; for instance there is 4 types of undead teams).
For an easier way of getting into bloodbowl, first read through the Live Rulebook on the Blood Bowl home page, then go here;
FumbblThis is an online version of the game. When the home page loads up click on the User Guide and read that
all the way through. Many people fail to actually read it all the way through, they skim it and believe that they've read all the important bits and then complain when they cant get it to work...
Follow the instructions in the Guide and soon you'll be creating your online team and playing people over the net! Its good fun.
If you want to give me a game any time, just let me know. I'm also Silas on there...