I've had so many problems with vistaprint, that I'd have to say moo, here.
Vistaprint is great for an average card. If you use their pre-made designs they seem to print everything fabulously. When I've used my own designs, it's 50/50. I've received cards that were cut poorly, printing had "bands", amongst other things.
If you have a KILLER design, I'd pay the extra and let Moo do it (I see they have higher end cards, too, and you can use things like spot uv!), to ensure it comes out correctly.
Basically, vistaprint for the basics, and just to "have" business cards, and Moo if you really want to "wow".