It's not a town in the mechanical sense, but I really love Mathiisen. Just something about the layout and environs I suppose, but I enjoy wandering around that neck of the woods.
From the list, Velyn Harbor is my favorite town in AD. Mostly for the aesthetics, but it's pretty convenient too, and usually not too busy. I enjoy the ruins in Woodhearth as well, although when I'm in Greenshade I tend to hang out in Marbruk more. There's just something about the Atlmer's attempt to establish what they consider to be a 'normal' settlement in the middle of the woods that I enjoy.
From an aesthetics perspective? Any of the High Elf towns, particularly those in Auridon as it has to be the most gorgeous zone in the game. Velyn Harbor is very nice as well, with a pretty convenient layout.
Rawl'Kha is great for convenience of bank and traders next to a wayshrine, but sucks for performance (trying to log in during peak with a character parked there can be frustrating), not to mention all the morons spamming abilities and dueling right on top of everything (they should restrict duels to outside of towns or have the guards attack players dueling).
Elden root is nice but not as convenient as Rawl'Kha. Often find myself porting to it rater than using the local bank and crafting stations as its so convenient.Elden Root is impressive and useless. Too much waste of time running around compared to Rawl'Kha. Also, Rawl'Kha guild traders have almost always better wares for sale. Proximity of outlaw's refuge, bank and stables cannot be shunned.