Now that I've got some opinions, I'll give my reasoning for thinking an Ace is more important in H2H than Roto. In Roto, your staff gets judged in its entirety. You could very easily stockpile 7 or 8 good (but not great) pitchers, start them based on matchups, and come out very good stat-wise. However, if you're in a good H2H league (that takes churning out of the strategy), you win or lose based on your consistency. You can't afford to sit 3/4 of your SPs in a given week, whereas you could do that in Roto.
Just my thoughts on it.
Disclaimer: Even in a Roto league, I still like to get an Ace in the first three or four rounds.