i'd probably use the MGM,the 9920 is at it's limit on 6s,although it's not a hot setup so it may well be fine.Were you going to use mechanical brakes? i think it would be a good idea,there was some concern about using motor brakes with the 24160,something to do with the caps used having a higher internal reistance,allowing voltage spikes to the fets under braking(or something),it was GriffinRU's theory,went over my head.
http://www.rc-monster.com/forum/showthread.php?t=5820