I really enjoy safetown cuz of the layout of the map itself. It is extremely unique in design and you can pretty much be anywhere and it has really cool rooms and other places to explore. Also has really amazing t traps and I just love the music that plays from time to time. I really cannot stand ns-streets at all because for one, it is ridiculously big and it is food for snipers( By food I mean innocents ready to be one tapped), and also it is really easy to fall off and lose your round and it gets annoying and don't get me started with the flying spaceships that can run you over as you cross certain pathways.
Since you didn't specified whether it has to be maps within SGM map pool or not, I'm going to say my favorites I have played on numerous TTT servers are ttt_mc_jondome and ttt_orange_v7. My least favorites are ttt_shattered_island, ttt_urban_ruins, and ttt_nuke_a1. But to remain on topic, my favorite map on SGM would be innomotel where my least favorite map would be either amsterville, craftroom, and mc_village.
Fav - Lost Temple. Super fun if Ts actually use the T traps, most people on this server camp spawn and die to a jihad so never actually get to enjoy it though. Least - All maps have their downsides but probably TTT_dog
