Definitely Neelix. There were so many times when I wished someone would flush him out an airlock!
Phlox seems pretty cool from what I have seen of Enterprise... but the idea behind the character didn't really sit right with me.
If Denobulans were such a close ally of Terrans in the early days of Starfleet why did we not see any Denobulans or even hear about their race in later Treks?
It was also implied in TOS that Spock was one of the first aliens to serve on a mostly human ship... and Enterprise just sort of ignored that idea.
If they had to make Phlox an alien, why not use an Andorian or a Tellarite or some other TOS species?
Other than that small nitpick, he seemed like a good guy. The actor who played him did a good job.