Both of them are former #1 Ring Magazine contenders, but that doesn't mean that they are comparable. LaStarza is one of the weaker contenders to hold that distinction, and Povetkin is one of the strongest.
At this point I think Povetkin's educated pressure (not to mention size) overcomes LaStarzas defensive prowess. I know some people will have Povetkin by blowout, but re-watching LaStarza I think he'd make it difficult for Povetkin. He's got a good sense of distance, and seems to me to play a game with his opponents, getting them to commit to a punch and then stepping back to neutralize it with distance control, while looking for an opportunity to counter. He also picks off punches pretty well with a parrying technique and again, looking for the counter. It wouldn't be that easy for Sasha, although I do think that he takes it.
Though I agree with your post I'm surprised by it J. You have always held that the champion, or a top contender is worthy of that place in any era have you not? Don't think I'm digging you out,btw, though I often disagree with you,I also often give you likes on here.
I think that being the #1 contender in any era, is a significant accomplishment. In my eyes that makes you a somebody, even if you took an easy route to it, and held it briefly! Having said that, the difference between the best and worst #1 contenders, is as important as the difference between the best and worst champions!