I'd recommend a new one.
1) You're guaranteed a Wii Motion Plus controller. Not a huge deal, but I'm guessing if you're wanting one at this point, you're wanting Zelda - which requires Motion Plus.
2) It's $70 more, but you'll get Mario Kart or New Super Mario Bros. - both $50 games and both worth it. Keep in mind, though - the NSMB bundles aren't backwards compatible with the GameCube games - so don't get one of those if you care about that. If you do get one of those, you can probably sell the Mario soundtrack that comes with them. Hell, I'd give you $7/shipped for it. If you don't want either of the games, they'll get you $20-$40 on eBay.
3) A brand-new unit with a 1 Year/15 month warranty through Nintendo. Not a huge deal, as has been mentioned, the Wii is pretty reliable... but still, a good thing to have.
4) 160 Club Nintendo coins. If you don't care at all about the various Club Nintendo prizes, they now offer downloadable games. 100 coins gets you Super Mario Kart ($8 value) and 150 coins gets Fluidity ($12 value). Or you can just sell the PIN code to someone who wants the coins.
I wouldn't suggest getting a used Wii for more than $50 at this point. $150 for a new unit is a pretty good deal - heck, if you're not in a hurry, it seems like someone is *always* running a Wii w/Gift Card promo.