operationally quite a lot of difference
You need to go back to the basics, the G450 is a G4 airframe plus WING. With different engines and a forward plug. Plane view was modified for the g450
The G550 has different wing, engines, and the plane view was designed for this model.
In general: different weights, different fuel loads, and pay loads.
Different speeds, fuel burns and range. Different coffee machines. The G550 is more runway efficient.
I suggest go on to Gulfstream sales web site, and check the published differences.
The two airframes actually handle differently, and any one who starts on a G450, will get into a little trouble if they fly the G550 in the same way, I know because it kinda bit me too.
glf