It's about scheme and player type IMO. The Bills don't always draft the best player on paper, they draft guys that fit what they want to do. And I guess that is why we see misses and things of that nature. I think it's a lot of luck, but teams like the Ravens just draft athletes, arm lengths, sizes, injury reg flags, and off field stuff be damned, and that's why it seems like they hit more often than others, I think they just have different standards than a team like the Bills who have very specific types they are looking for.
The Bills are the picky guy at the bar at 3 am who may go home alone. Teams like the Ravens always seem to get lucky because they are open to anything.