Sure you can be ecstatic when guys like Newton/Manziel/RGIII run around for 100 yards 1 week, and that is exactly what puts them as overall top5 QB's at years end, but the inconsistencies are there for you to worry and second guess who should be behind him and guys like that. Give me a consistent 18-22 point game from Ryan (with a healthy o-line), Rivers, Brees, hell even Cutler over a guy who goes 19.14, 12.7, 12.58, 15.10, 34.06, 14.3, 5.24, 12.23 any day of the week.
Thats 13.06 points per week on average without the high 34 point. Including that high game, bumps him up to 15.68 per game. *not including week 1 he missed. Give him 13.06 for week 1 lets say and that puts him at QB11 for the year instead of 15. *All based on 1point for 25passing yards, 4 TD, -2 INT, 1p for 10 rushing yards, 6p rush TD which I think is standard.
I'm beginning to want absolutely no part of Newton or guys who are similar and rely on rushing and can't throw as well, for pure inconsistency.
Manziel on the other hand is completely off my list to ever own.
Consistency is pretty much irrelevant. The guy who scores more fantasy points will help you win more head-to-head games over the course of a season even if he's much less consistent, unless they're within a couple fantasy points of each other for the entire season. I ran some numbers on this at some point, and the result was something like: over the course of a season, an impossibly consistent player who scores the exact same amount every game is worth about 5 fantasy points more than a wildly inconsistent player who only has huge games & duds.
Also, if there is a difference in consistency between running QBs and pocket passers, it's pretty small. Since the start of 2012, Newton has had 5 games where he scored under 10 fantasy points (he's averaged 18.8 ppg). Brady has 5 (and 18.3 ppg). Ryan has 5 (and 17.3 ppg). Stafford has 6 (and 17.0 ppg). Wilson has 5 (and 17.9 ppg). Kaepernick has 4 since he took over as starter in mid 2012 (which puts him on pace for 5), and 17.4 ppg. Manning, Brees, and Rodgers have mostly avoided single digit games (they have only 5 between them), but they're also putting up bigger numbers across the board (about 3 ppg better than Newton, on the whole).