No you do not have to choose one or the other. There 21 Soviet commanders and 10 of them do not have either.
And the "compete" logic is simply flawed, since it has to do with diversity and not balance.
Actually there is balance which has to with how unit and faction compare with each other and there diversity which has to do with how units with in the same faction compare to one another.
Lets say we buff Shock to the same power level of Guards making them equally cost efficient but now they compete with PPsh conscripts so now we have to buff PPsh conscripts because no one uses them but then we have to buff penals because no one uses and you end up with OP faction.
In the end you have messed up balance vs other faction in order to fix a diversity issue.
Look, I'm not saying that shocks need more adjustment but they DO compete. If they are equally attractive THEN we have diversity, if not then we don't. Soviet have 21 commanders, how many have shocks and guards? How many are similar enough that the choice of one or the other dictates putting it into your card?
The isu commanders for example, I personally much prefer the one with shocks because of vehicle detection BUT guards are a great unit so I usually go that way instead of the cqb unit in a long ranged combat game. They don't fight each other but are competing. Their balance is independent of one another but their attractiveness is not.