That really depends on your uses and how much you have to spend. If you're on a budget, then the used MacBook wouldn't be a bad idea. If you have the extra money and are willing to spend it, the extra features in the MacBook Pro could be worth it. It will come with 4GB RAM, 250GB HDD, 2.4GHz processor, backlit keyboard, roughly double the battery life, SD card slot, FireWire 800 port, and a better GPU and screen. So you do get a fairly nice upgrade if you go with the Pro.
It's a wider color gamut, and slightly better quality, so it just looks nicer. Also, you can only put a max of 6GB ram in the MacBook or 8GB in the MBP
Would also depend on which screen panel was used in that MacBook. The first ones sold for the first few months of release had 3 or 4 different panels. One of these was a lot worse than the others. I cant remember off hand which panel it was but a bit of Mroogle would tell you