High population shards vs. low population shards (and the considerations of shard consolidation) bring up some odd things, when you look really close at it.
The big population shards have positive things about them, such as the big economy, and on the Tram side there's lots of people to do peerless and other activities with. But, on shards with populations like that, the available housing space doesn't support the population perfectly. It's hard to place in tram or fel and big plots are for sale by players at inflated prices which are indicative of the mismatch.
The housing situation that exists now on, say, Atlantic, is way better than we had it in like 2000. Today's mismatch doesn't compare with the hell we had back then, but on the larger population shards housing space is IMO scarcer than would be ideal.
Low population shards have open housing spots and that alone can make them appealing. A downside is that so much less is happening in terms of people just getting together and doing stuff.
Even though I do a lot of Felucca stuff, I don't know exactly how the high-population Felucca champ spawn scene works out in all of this, how it's affected, and so on. The housing situation is mirrored within Tram and Fel, however.
I consider the creation of the troublesome housing market for a consolidated shard to be a downside to doing that. There are other serious issues, such as, which version of Luna gets kept? One could re-build this new shard to incorporate 2 lunas (rename/recolor one), and well... there are ways to deal with the lost real estate on the one shard but they are all very involved and labor intensive on the dev side. Right now the shards are, on a basic server and client level, identical, except for various GM-added items and so on. Changing it so that shards were fundamentally different is significant.
It's kinda easier to just leave low population servers up and running than to really, seriously deal with the complexities of keeping people happy during a shard consolidation.