We started out in Fenris because the game assigned us there. But it was too crowded. We haven't been back since the beginning. Our highest character there is a lvl14 orc shaman.
Then we started a new gang on an Oceanic server, Dath'Remar. It's loads of fun playing with Aussies.
Then we discovered an Uncle and Cousins on Kilrogg, so we started a family there.
But my little guys kept wanting to start new characters. So we randomly picked Drenden next. The Drenden family tended to be mostly Alliance, while the other servers were where we'd play the Horde. When my niece came for a visit, though, she stared her Tauren Hunter, Nellesgirl, on Drenden. It was the only place we had room.
Kilrogg's population: a huge number of lvl 70s and a very even, but low distribution of everyone else. Mostly alts and friends and twinks of the 70s, I assume. I think the economy, at least on the horde side, reflects this. Anything leather with + agility below level 40 is very pricey, especially "of the Monkey." Mageroyal, Peacebloom, and linen cloth are dirt cheap.
After studying the Auction House for a few month last summer, I wanted to see how the economy worked on a lower population server. Enter our group on Velen. The last time I checked, and it has been a while, Velen had a lump of 70's but also a nice curve of 1-20s, which trailed off into the 30s and 40s. I'm sure it's changed now. But I did learn what I wanted to learn about different server economies and how much it depends on the distribution of levels.
If I can generalize, based on my own observation on four different servers: On a server with mostly 70s and a low but even distribution of everything else, prices for low and medium leather gear is very high. Imagine paying 2-3 gold for a level 7 green with +1 agility? And replacing it again in two levels? Savory Deviate Delight runs 15-18 gold a stack. On the other hand, the same piece of gear on the server where the bulk of players are under level 30 or over 60 is only going to be 10 or 15 silvers or less. And SDD is only 3-4 gold per stack.
On the other hand, low end raw materials such as copper ore, silverleaf, or light leather are less expensive on the former server and more on the latter. Which means that for someone just starting out, it is going to much easier to make money gathering and gear will be much less expensive and a low population server. But it will be take longer to save up a big wad of cash for the mount at 40. On the high population server, gathering is not going to be as lucrative, but leather greens with "of the monkey" or "of agility" will bring a pretty penny at the auction house. It is much easier to make a 100 gold on one of these servers, I find.
Next time, I'll post my surefire method for getting to the level 12-13 with a few gold in your pocket and a steady income. No grinding or gathering. You won't be rich, but you'll be able to afford all of your training, plus a decent weapon and a few reasonably priced greens.
And how to make decent money as a low level enchanter. No kidding.