Steve Swallow started out as an upright bassist and switched to electric bass played with a copper pick employing upstrokes exclusively. Crazy. If it sounds wierd, just check out the latest John Scofield live album that Swallow plays on. Wow.

I'm gonna buy some copper picks!
Also, check out Mike Gordon, Chris Squire, Anthony Jackson (He uses both, but you will be able to pick out where he uses a pick.), Carol Kaye, Scott Thunes, and the great Sir Paul.
BTW, +1000 in regards to everyone who said try both and choose which one is right for you. It helps to be well versed in both techniques.