Is GSX easier on the FPS than default airport traffic? 

 

I found default airport vehicles to be harder on the FPS than default AI traffic so I turned it right to zero but it's getting a little dull without it. Plus they bounced all over the tarmac like they were possessed.

Hiya, GSX doesn't add airport traffic, it adds baggage handling, catering trucks, fuel trucks, passenger buses and follow me vehicles. Any airport vehicles are generally added with whatever airport addon you are using.

And to your question there isn't  a much of  a hit on fps using  gsx  you probably  wont know any difference

Yes, there is no FPS hit at all, even on medium machines. It adds above mentioned vehicles ONLY around your airplane, so if you are using default airports you will not see any of these until you are close to the chosen/assigned gate.

3-5 FPS drop in my case together with increased CPU usage is what I see with gsx. Tbh I think it's normal and wondering how come no one else looses performance

Well, to be honest, in my experience, it's not completely true that there's no performance loss. I don't experience any framerate reduction, but there is definitely an increase in delayed texture loading. I have noticed, when using the NGX, that when all the vehicles are doing their thing, moving from a VC view to an external view there is definitely the classic skeleton fuselage that takes a lot longer to load than without GSX.

I cannot see any FPS hit at my medium hardware.

nor here using  gsx

I see a drop in FPS during pushback.

I have not noticed a drop in FPS using GSX. 

GSX does not cause any issues on my system