Your 100pts/25yd example only works because it (dramatically) increases the drop off within the position. Which is ookook's point.
Exactly. Sure, if you multiply scoring of a position by a constant, it will increase the dispersion of players' projected scores (e.g., the standard deviation will go up) and the drop-offs will increase. But 6 pts per TD does not have a very marked effect on this, and I have yet to see a scoring system where QBs get MORE than 6 pts (not saying one doesn't exist, but I have seen many hundreds where this is not the case). Sometimes there are large bonuses for arbitrary amounts of yards passing which does this some. But these are not all that common or sensible.
Personally, I think that if one does not increase value of QBs by starting 2, then the socring system SHOULD give more points for passing yards, but in a more linear fashion than bonuses. 6 pts per TD, -1.5 per INT, and .075 per yard passing (increased from the common .05) seems to work well. Drop off increase and then weighing when to take a top QB is more meaningful decision.
But absent either start 2 or .075, I almost always wait (obviously 14 man roster might change this, as noted, but might not).
I realize that many FF owners like taking early QBs. And sometimes one I think will do well falls a couple rounds and I pull the trigger; for example I got McNabb in the 6th a couple years back and I had him projected at QB5 or so and thought he shold have gone in the 4th. I planned to wait until the 8th but he was there so I took him and never had to decide WDIS.
I guess someone should note that an advantage to QBBC strategy is that if your top QB, RB or WR goes down you are not out for the season. That is, if in a 1QB-2RB-3WR-1TE league I take 3 RBs and 4WRs before I take a few QBs, my backups are always closer in value to my starters. The downside is that you have traded some QB starter value to have this insurance, which is sitting on your bench when there are no injuries. Is a trade-off, so I see taking a top QB as more of an all or nothing gambit.
So when would I take Brees or Rodgers in 6/TD league if they were sitting there? Mid to late 2nd round. But they won't be.