Personally, I wouldn't go with a mac. I like pc's better, and they're a lot cheaper for what you get. What price range are you talking about? Is this for hobby or profession? Obviously, if you want to make a job out of this, you're going to want to spend more money and get a better one. I have a pretty cheap laptop and it runs fine, but I'm just doing basic hobby stuff. You'd want a much better laptop if you're more serious.
I regard my computers as tools and don't care one way or another on the Mac versus PC debate, my choice is based entirely on what software I want them to run. There's not much software that isn't available for both Mac and PC, but there are a couple of things that I use which are Mac only, plus Macs can be set to dual boot to give you windows on the same machine. (It's probably unnecessary to say that I use both Mac and PC).
PCs cheaper than Macs? It's true that you can get PCs a lot cheaper than Macs, but are you really comparing like with like? If you want to do serious work, you'll find that USB just doesn't cut it, you need firewire (and preferably FW800), plus I use the ExpressCard slot all the time. Also check out the display adapters, processor speed and memory and you'll probably find that the level of PC Laptop that gives you what you need isn't so much cheaper than the equivalent Macbook after all.
I'd say, decide what software you want to use, look up the technical requirements on the manufacturers web site and check what people think in a couple of forums before you make your decision.