I've recently been trying out World of Warplanes and War Thunder.
So far I prefer War Thunder. Main reason is you get less ramming with War Thunder. It's easier to avoid rams in War Thunder because the planes seem more realistically scaled to the environment. In World of Warplanes the planes seem oversized. War Thunder seems to be less reliant on irritating hitpoints when you damage enemy aircraft. The graphics are nicer to look at in War Thunder too. But World of Warplanes is in closed Beta. It has already improved a lot since last summer when I first tried it and it may improve more before it goes to open Beta.