G5 is very impressive in versatility (flight, massive buff to enlargement, elemental manipulation, environmental control, malleablity, toonforce body manipulation of opponent)
and defense (zoan durability/regen, molding to weapons to take reduced damage, toonforce regen bouncing back to normal)
and for brute strength (it allows him to do freaky stuff that no one else in the series can even come close to (effortlessly swinging dragon kaido around like a jumping rope).
Luffy is still learning what his fruit can do and is less practiced and disciplined than he is in base/G4.