There are eight tier IV tank destroyers (as of patch 9.15):
SU-85B
Hetzer
Marder 38T
StuG III Ausf. B
M8A1
T40
Somua SAu 40
Alecto
It was difficult to choose the best one, as I said a while ago. If you ask almost anyone, they would call me mad or at least an idiot, because the Somua is a hated tank among a lot of people. But I did very well in that tank. My WN8 rating when I sold it was 2,038. Part of this is because I played it somewhat recently, after I had learned a lot about the game. I played only 17 battles before I sold it, but during those battles I had a win rate of almost 59% and got (at least) one Ace tanker game. Even if I should declare this as the worst tier iv tank destroyer, I can’t, Or rather: I will not.
There are eight tier IV tank destroyers (as of WOT 9.6):
SU-85B
Hetzer
Marder 38T
StuG III Ausf. B
M8A1
T40
Somua SAu 40
Alecto
To choose one from these is actually very difficult. They are all good, or at least not bad. The Somua gets a lot of criticism, but when I played it, I did quite well. I only played it for 17 battles, and got a win rate of 58,8%. The T40 was the one I did worst in. So, in my opinion, the four strongest of these are the Hetzer, the SU-85B, the M8A1 and the Alecto. But they are all quite different to play:
The Hetzer has got a derp gun, which is quite fun. You will one shot every tier II and III when you are a top tier. You can do quite a lot of damage also on tier V and VI vehicles. The armor is very sloped, so you can actually use it as protection from some tanks.
The SU-85B is all about the top 85 mm gun. Good penetration, good alpha damage and not to inaccurate.
The M8A1 has a turret and is very fast, so you use it quite differently than the others.
The Alecto also has a derp gun, and is a lot faster than the Hezter. However: The armor is non existent, by 10 mm.
So these are very difficult to choose from. I never sold my Hetzer, and I rebought the SU-85B as a crew trainer. I played the M8A1 a long time ago, and I believe I might enjoy it more now, as I’m a better player now. But since I have to choose only one, it has got to be the Hezter.
Pros:
The derp gun with HE-shells. If you penetrate, you do 410 damage. Since it is HE, you will do damage to modules and crew even if you don’t penetrate.
The armor is better than the competition, since it is very sloped. You are NOT invulnerable, but you will bounce some shots
Low profile means better camo rating
Cons:
Derp gun is inaccurate
It is slower than many of the other tier IV tank destroyers, and the traverse is also not the best
wotnewbie 