Which xpac are most people playing now?

I started playing again a couple of years ago and got pretty seriously into it for about 6 months. I played a lot on steam and got to about 1850 before I downloaded Voobly however I ended up quitting before I ever really got into playing there. SO, I've been out of the game for a while now but I want to start playing again.

I know a couple of expansions have come out since then and I'm wondering if the majority of competitive players are still playing the conqueror's or if they are actually playing more of the new expansions for once? Also, which expansion would be the easiest to get games on/is most alive?

Thanks