I'm talking mostly about scope.
For example, as far as I know, the AMC TC has had the largest amount of contributing mappers.
James, Mikko, Micky C, Rusty Nails, Mike Von Skellington, Davox, Forge, Rhaisher, Sang, Loke, Highwire, Zaxtor, probably a few others I'm forgetting, soon-to-be Merlijn and Gambini.
It definitely has the largest art set. The eduke32 art limit was doubled specifically for this TC.
The only thing I'm not sure about is number of levels/play time. Between Episodes 1 and 2, you've got around 20 hours on first play through. I can't recall exactly how many there are, but I know that Zaxtor's Oblivion is quite large.
The detail level can be a bit variable at times but is usually above average. SST on the other hand has relatively low details by today's standards, however still pulls off a pretty good look, plus has great atmosphere and level design.
I'd also like to think the levels are among the most ambitious in the Duke community. I mean how many TCs having you falling several km towards a martian colony.
Not to mention all the really deep gameplay features like the exporable hubs between levels as well as research/upgrades and things.