The reason you see the SS5/6 on their tree is due to the fact all nations are getting
SS5/6's. We are just getting to see theirs first.

this means there can only be one use of soviet subs... flag hunting... and they can
do it nice perhaps

since they are not effective against both subs and bbs

i heard they are adding ss5 and ss6 in USSR,if so,then pro is that it have more ss,if
not,welllll....i dont know what else to say

If they aren't change from test server ...

Pro : highest speed (some tier(?) faster then KM)(normal speed , surface speed cap
is 40knt , too) , longest submerge time (same with IJN)
Con : worst SS torp + less torp lunchers + no proxy torp = worst damege output