The GIV isnt widely used in Europe as the previous owners have usually upgraded, but with the right equipment, it's an awesome aircraft and extremely reliable. There are limitations and gotcha's such as the new European ATN for CPDLC.
As for pilots, they are available but like everything else associated with the Gulfstream, they will cost more than the Challenger.
The first question that you have to answer is what is your mission, for most European missions the Challenger will be sufficient, but not for longer trips, sometimes logic doesnt play a role as the owner just wants the wow factor. Then it has to be the Gulfstream
