This is such a stupid conversation - it's only got traction because of how Drummond's rookie season has played out, in spite of arguments for him being the BPA at the time.
8 teams passed on Drummond. Maybe half of them would have taken him now, in hindsight (for sure Sacto at #5 instead of Thomas Robinson) making the whole argument moot. If the Raps blew it at #8, then Sacto really blew it at #5, which means if we're gonna argue shoulda/woulda/couldas, Drummond wouldn't even have been on the board at #8.
As has been explained pretty well above, there are much, much bigger draft day blunders than taking Ross over Drummond.
Also, after 1 (1!) season, it's way too early to make final judgments on either player. Drummond's attitude may catch up to him yet - even Michael Beasley's had a couple nice seasons.