The Enterprise uniforms from the 2009 reboot. TOS + big budget + full length pants = winner.
If it weren't for nostalgia clouding my judgement, I'd go for the realistic and practical uniforms worn in Star Trek: Enterprise.
I've never been a fan of any of the TNG TV uniforms. I used to like the First Contact ones, and they looked cool in the movies, but I quickly grew bored of them in DS9.
The Wrath of Khan uniforms look like good dress costumes, but seen impractical for day-to-day wear. Plus they make everyone look like Space Mounties.
All-time worst has to be the alt-future ones seen in "All Good Things," "The Visitor," "Endgame" etc.