Just bought the Gamo .
I was in exactly the same position.
Have a look on YouTube there is a video doing a direct comparison.
I find that the Gamo shoots low and you cannot adjust the sights .
I have just bought a tactical rail and holographic sight , so roll on weekend when I get to give it a blast.
CO2 semi autos in my opinion will not clover leaf but you can get a reasonable group down to size with practice.