Well mainly because I have the M1s and not M1.1s one the brain LOLJack, curious why you list the 10 series for CH and not the 1?
The 1.1s, I1s and A1.5s have their balance more towards the 10s than the A1s and M1s. The latter can still be made to increase grip by goosing up the gain (more effective and better sounding than increasing feedback, trust me) but the limits of power storage capacity of the old models would still remain. In my case I leveraged room gain more than I normally would. With the 10s I'm back closer to my old speaker positioning.
For people who don't have to deal with sealed bass like we do this is not an issue, like say Gian. Those of us on Magico or VSA Ultra 9s or 11s I would recommend getting the .1 upgrade or space and funds permitting go 10 series.