is bowman better in coverage than willis, Making him the preferred lb against the packers?
No, it's the other way around. When the 49ers are in their nickel packages, Patrick Willis is the one assigned to coverage - whether it be a tight end, running back even a wide receiver. When they go to the dime, Perrish Cox takes over that role. That's why Fangio has called the nickel cornerback role a quasi-linebacker assignment - because he's taking the place of a linebacker.
Willis and Bowman were alternating on the series on which they would leave the game when Cox entered. It just so happened that Packers had longer series when Bowman was in the game and Willis on the sideline. By my count Cox substituted for Willis 20 times on Sunday and substituted for Bowman 11 times.
Read more here:
http://blogs.sacbee.com/49ers/