In my opinion after recentely using M95 on quite a few cars, I would choose M105.
In comparision to each other...
M105 has more cut then M95, in terms of defect removal after an application. M105 also breaks down in 5-20 seconds a wool pad, where as M95 has a more traditional working time (much wetter) and breaks down in 30 seconds or more. The cut difference is small enough, but M105 is definetly more aggressive and does the job much quicker.
For the amount of cut M95 has (it has a lot, just not quite M105 amount) it does finish down pretty nice, but nowhere near as nice as M105 (when worked properly and quickly).
M105 is much more finicky and sometimes is just a pain in the butt to use. It can smear, gum up, be stubborn to remove basically when ever it wants to. M95 by comparision is much more user friendly.
If you could only have 1, then M95 might be the better choice because it has consistant results, where as M105 can act horribly on certain cars. However, when M105 is on, nothing touches it, not even M95 IMO.