I also have both. Each has its own purpose, abilities, and stamina. I have trailer hitches on both and fold down work platforms instead of a back seat. In winter, electric (EZ-GO) is better: weight for traction and ease of initial movement. The gas (Yamaha) one in winter is a bit stubborn to get going even with the choke. For long distance hauling around my back trails (1-2 miles) I feel better about chosing the gas one. I've pushed the electric one home just once and that's enough.
However, two days ago, the gas one's fuel filter got plugged with water and would not start. The electric one easily pushed it home with the steering wheel strapped to strait-ahead and the bumper nose on the gas's trailer hitch. I could steer them anywhere using this technique.
When its battery time, I'm going to try 4 12v deep cycles instead of a full complement of 6 8v batteries for cost reasons. Costco sells cart batteries, too, which is how I got my current set. You have to check the water levels all the time in the EZ-GO. For some reason, the charger rate causes a lot of water loss.
I bought junk carts and easily keep them going. A local cart repair shop services golf course carts and many parts are free from him (as in tires). My cart tires seemed to have a problem with slow air leaks around the valve stems at the wheel. I used some tire sealent glue on them and so now that problem is solved.
I have a Yamaha 4 wheeler that now sits idle because the carts start almost immediatly, have lots of leg room, kids can run them, dogs can ride on them, they haul trailers and are quiet.
Only one problem ever: If you are pulling a snowmobile trailer with 30 bales of hay on it, you have no brakes to speak of. EZ-GO but No-GO stop-oh.
By the way, we have lots of steep side hills on the trails, gas one maybe, but never a problem with potential rollover with the electric cart.
That's my opinion and I'm unanimous with it.