I do think difference between 10 and 12 teams leagues is crucial here. I would be willing to let 10 QBs come off the board before taking one in a 10 teamer to gauge how QB crazy my draft is going to be, because I'll still be able to come back and get two very solid QB2s in any scenario. QB is 24-25 deep and maybe more if the rookies emerge in camp/preseason. In a 12 team league, there are likely going to be more picks between your picks (draft slot is also important info, picking at/near turn makes it harder to time picks). So you might be looking at CK/Romo when you're up, but if you pass, that turns into Cutler/Freeman at the next pick, and then you're looking at Schaub/ASmith at the next pick.
Don't get me wrong, Cutler/Schaub is far from a disaster at QB in a 2QB league, but in a 12 teamer, the WW will start out and remain picked clean, including pre-emptive options. You'll have more competition for Manuel/Smith/Locker types later in your draft. It's just a more fine line to walk. Also, you're likely to see less erosion at RB/WR/TE between picks if QBs are coming off the board fast anyway, so you are giving up a tier or more at QB while RB/WR/TE is not degrading by a tier or more between picks.
Don't get cute with it in 12 team leagues. Get 2 top 12 QBs in the first 2-3 rounds. If your opponents are slowplaying QB, then pick off another solid QB2 in say the 6th. Do it again in the 8th/9th if they are still dragging their feet. Solid starting QBs ALWAYS have trade value in a 12 tm 2QB league.