All depends on what you need to use it for. While all Macs are very nice computers (very fast, come with great software, etc.), some are more powerful than others and offer other hardware features (e.g. the MacBook Pro has multitouch, LED screen, etc.).
Just the standard MacBook is a great choice for starters. It's the least expensive Mac notebook right now, and it works very well. But if you think you need some extra "oomph", certainly a 13" MacBook Pro would take care of it. It all comes down to how much power you need, and how much you're willing to spend. Either way, you'll end up with a great machine, far better than any PC you've ever owned.