As a starting resident of Taurus back in the day and now an Aries resident, I can say that both servers are populated enough that you can find support if you need it and there are still people willing to play together. Only issue of course is that, as said before, economy is down the toilet. Taurus is slowing getting to, or rather is at the starting point of IM selling only. Aries is definitely the most populated and if you're looking for a large number of people to play with, Aries is your best bet but I'd only recommend it if you believe you can manufacture and acquire items and armor on your own as the prices in Aries are like a stick through your a** bent at the throat with lemon juice covered splinters. Oh but there is Taurus and I personally know that the community there is nice enough but it is kinda slowly dying, kinda why I moved to Aries. I had the means to support myself so I don't have to worry about gold and a good alchemist character is all you need to survive in the equipment department. There are tons of people selling lots of services (JS,DS,FS, etc...) and if you start up any high level instances, they'll get filled up pretty fast. Lots of fun things happen at SB like random gold drops, photo ops, and other stupidly fun stuff.

That's only my opinion of course...