I currently don't own either but would suggest the best answer is BOTH. Solar for when the sun is out in full force and they're not shaded by trees, a genset for those times the weather is heavily overcast or your site is in complete shade.
FWIW, I have owned 2 different EU2000i gensets, a great unit, but still way too noisy for me in any organized campground. You gotta fuel it obviously and regardless of what some may claim it does produce exhaust fumes that smell. But it will reliably recharge your batteries regardless of the weather.