Generally speaking across all the series, I like the TOS uniforms for wear aboard ship.
Getting more specific, I like the idea that starfleet would have something practical and comfortable for shipboard wear and deployed away missions like what we saw in ENT or TOS. The monster maroons from the TOS movie era would make passable service dress uniforms for ashore wear on Federation planets or diplomatic functions; as shipboard duty uniforms they are beyond impractical.
Although I thought the pajama uniforms in TMP reeked ass, Kirk's initial 2-tone admiral's uniform was one of the smartest we've seen in all Trek.
TNG-era uniforms were all okay, but I wish they'd stuck with the same department colors and stripes that TOS used. There are some really good fan-made variations on this theme, that sort of mix the old and new.