Great Post!
You better though add that CycloDS is not DSi compatible.
Also, I think M3Sakura is hardest to theme for (I actually only made simple convert of sakura theme to moonshell 2 way back) - and that was... not easy... But if you are happy with just own wallpaper... BOOM, sakura wins the round.
CycloDS may be simpliest one (so is the firmware),
Acekard is in middleline, and gives the maker choices of what to include, and what to not include to skin. Photoshopping stuff is hurr.
Oh, also, I heard M3 cannot be bricked, you can just reflash it (Just what I heard and read though)