It's the Nameless. The Edelweiss seems to have a better reputation and I don't really know why. You have tons of fast mediums and lights at that tier to pick from. The gun is great yeah, but you don't get to run a Vertical Stabilizer and, unlike the Dragon, it actually makes a difference on that one.
The Nameless has all of the typical heavy tank characteristics. It has a pretty good and small turret, a good frontal plate, and decent but not amazing speed.
What it does have: A gun that hits for 300 damage and reloads like a horny rabbit.
It has a turret traverse that prevents ANYONE from toying with you.
It has mobility to reverse in and out of positions quickly and to reposition itself faster than an IS could ever dream of.
If you ever see a Nameless, get a Nameless.