i ride both almost everyday, everything you posted initially warrants downsizing to a 550.
Downsides of the 550, not a very large or heavy bike so the wind can be an issue if its strong that day, not great for passengers.
Not gonna lie tho, somedays it feels like the 550 has the same footprint as the 750 as far as taking up space, or being difficult to move around the shop....a little less weight, but still the same kinda struggle....drastically different pushing the bike if when it dies though...pushing a 550 is no sweat but a 750 is real work.
the 550 you basically need all 5 gears for normal riding, the 750 lives in 3 or 4th. - more shifting and throttle work, fuel capacity kinda sucks in my opinion, maybe its cause i do so much highway commuting and ride above 80, but i fill up the 550 a lot, they also need more chain maintenance than a 750.
I cant really see myself not having one of each though.