If you mean Fabius GS Premium then the fundomental differences are.

1st) Flow meter.
The Fabius Plus has mechanical flowmeters with, and the Fabius GS premium has electronic indications with a single flowmeter for the total gases.

2nd) Size

The Fabius GS premium was created more for the US Market where they wanted Big equipment.

3rd) Fabius plus has other than the trolley version the wall version and the celling version and Fabius GS premium has only the trolley version.

Other than that there are doing excactly the same things.

Same ventilation modes
Same configurations
Same piston Ventilator

also try to have a look at the FABIUS PLUS XL.

I thing A5 from Mindray is only available in the US market and had a lot of recalls

http://www.fda.gov/MedicalDevices/Safety/ListofRecalls/ucm330242.htm

http://www.fda.gov/Safety/Recalls/ucm327976.htm