Done E55 to w212 e63(Daves old modified one even more modified!) back to e55 then to a w213 e63s
very very different beasts
E55 - by far the comfiest of all 3, power is usable feels like a small car still which is a positive. you know the e55 so won't say no more!
w212 e63 modified - absolute beast, still feels like a small car and a well spec'd one gave loads of toys. did get tail happy as were only rwd, but still handled well.
E63s w213 - has best of both worlds, driving in comfort is like the E55, usable power but can be a little laggy. I have the sports seats and even though less comfortable than the e55, still wouldn't call them uncomfortable as still felt good after a 11 hour drive to stuttgart. Sport mode is the best mode for daily city driving as throttle response is faster and just feels more planted. Sport Plus you get the lot, super fast, pops and crackles and the thing is lightning fast! the w213 feels a lot bigger than both the others and Dave mentioned the crabbing which only really shows its face during cold spells. you won't be disappointed.
that's a very very quick review of them.