If you're going to use fusion, you'll probably not want to go with 1GB of RAM which is what you get with the last-gen macbook. That's another reason to consider getting the new one, or alternatively you could get a memory upgrade - but be sure to get it from a third party seller like crucial, not from Apple, to save money.

I have no trouble with Fusion, except for playing some old games, but I have 4GB RAM. I'm not sure if the 2GB you get with the new MacBook is enough.