You could always make level 1 toons on the servers you are interested in, and the faction you want to play, and ask people on the server how it is.
A thread below with a couple of people who have moved to lower pop servers, might be worth asking in there how things are for them now they have levelled a bit.
Remember the stat sites are showing probably a tiny percentage of each faction, ironforge.pro is only representative of people who have raided, I checked. Not everyone plays to raid so they might not be quite as lopsided as they appear.