Russian factions are my favorite in TW games (with a strange exception to M2TW) for a number of reasons.

First off you've got a lot of open land to yourself. With some speed, some military skill and a bit of luck you can lock down vast tracks of land in no time flat.

Once you've got the steppes secured then there's numerous opportunities for expansion. Will you sail over the black sea and attack the stagnant Byzantines? Harass the Turks in Georgia? Invade Poland / Hungary? Perhaps even an invasion of Scandinavia!

I love playing in Early so by the time my empire is really big and i'm facing numerous wars, I've got to really start thinking about the Horde. If you're not careful you can easily ge bogged down fighting the West while the Horde looms ever closer. It's a tough spot to be in, and all great fun!