The Bills had 394 1st and 10's plays in 2011. I took out spikes, kneel downs, waived off plays due to penalty.
Here was their run pass ratio
52% (204) called pass plays (Sacked 6 times, Scrambled 12 times)
48% (190) called run plays
For the NFL as a whole, it was 50.1% called pass plays and 49.9% called run plays.
So while the Bills threw the ball more than average, it was only 2% more and the NFL as a whole is almost perfectly balanced on 1st and 10. Pretty interesting if you ask me.