Time for pros and cons
:
T-34:
-Faster
-Cheaper
-Might get vet fast
-Less accurate IIRC
-Weaker
KV-1
-Stronger
-Can plow over obstacles
-More accurate (possibliy)
-Slower
-More expensive
-Might get vet slower
-Less vunerable to shrecks IIRC
On maps that have less fuel, you'll want to go for the T-34, as its easier to obtain and if you lose it, it wont tke as long to get a new one. However if you anticipate heavy tank resistence or you want to plow through the enemy lines, you might want the KV.