ORIGINAL: morvael
IMHO the cavalry bonus for Soviet cavalry is not necessary at all. Time of being elite formation passed, these were regulars like rifles. Especially if one considers the speed with which these formations were wasted, destroyed and rebuilt.
think the problem is they were mixed, goes back to the civil war and Trotsky's 'Proletarians to horse' speech/order. A lot were raised effectively taking recruits from rural areas (who could ride horses in non-combat situations) and expecting them to do so in a complex modern battle. On the other hand, some formations were raised from the Cossack and Central Asian populations to whom going to war on a horse was pretty natural.
Its clear that up to mid-1943 the Soviets didn't especially value the cavalry corps. They were there to offer a bit more mobility and often used to try and disrupt the German defences .. if they failed well so what seemed to be the mindset. With the emergence of the cav-mech concept they gained a clearer role, primarily as an exploitation not a breakthrough formation.
The problem is in the game they are breakthrough formations, those extra MPs plus decent CV makes them too valuable. I have an army in my current game with 4 Gds Cav Corps and by cycling between them I can easily generate an attack stack of about 22-25 with MP of 16+. That will take apart an isolated German infantry division or in combination with other units push back a stack or one well dug in. I actually think they are too strong, but can understand why Chaos45 opted to build a slightly gamey army around them (playing Pelton I can see no reason not to fully exploit the rule set)