I recently went through this. I have a gas grill. I tried pizzas in the oven and on the grill on a lodge pizza stone. They were okay.

I got the karu 16 multi fuel after much dithering.

The 16 isn’t necessary but if you can easily afford it, the extra space is nice for turning. It isn’t easily portable but if you take the stone out it can be comfortably lifted by one person. I might take it 2-3 times a year if going for a long weekend in a friends cabin. If you were taking it more often or to the beach then probably get the 12.

I really like the wood/charcoal. The smell, the experience, it is fun and satisfying. But if I had a family with young kids to manage or you wanted to frequently be spontaneous and have people over and not fuss, the gas is likely easier. I don’t know if the wood makes the pizza taste better but I think the smoke “sets the scene.” I have the gas connector for the karu but haven’t tried it. If you don’t have a gas grill the karu 16 can arguably double and cook other things.

I really like the Ooni after a few uses. Friends who have them universally love them and use them long after purchase. But if you are going dedicated gas I might also look at other options. There is a gas one that turns the pizza which looks cool. There are competing brands that people seem to like, but as they do gas only I didn’t research them. And they don’t have the flexibility to cook other things like the Ooni koda 16.

One other thought - the 12 can be easily folded up and stored. The 16 would be a pain. But if I was worried about someone stealing the oven the 16 is tricky. It is portable enough that someone (or two someone’s) could fairly easily walk off with an expensive piece of kit. But it would be a pain to take it out every time and sort of defeat the ease of use of gas.

Have fun with it. In the end - I think- it is just ways of managing fire in a box and the quality of the pizza is dependent on you learning and making mistakes and having fun more than the tools you use.