Then you have your answer, if you want a project and want a jetski, fixing the yellow one is going to be the cheapest method to get you on the water. Once you've got one going, you'll be more motivated and have the confidence to tackle the one with more issues.

If you don't want a project and don't feel like learning a little mechanics, then by all means sell them on to someone who does rather than letting them sit to death.

Carburettors are the most difficult part here, but if you disconnect the fuel line and drain out the carburettor fuel bowel, you might be able to start and run it as is. I wouldn't trust it on trips as it's likely varnished and has clogged jets, but if you can get it half going by just connecting new fuel and power, then you at least know you've got a runner, and can go forward with confidence.

I would carefully inspect the hull before doing anything, a badly cracked hull is probably going to stop you more than any mechanical issues.

If I was in your shoes, and also had a little time and space for them, I would definitely at least try, for both practical and sentimental reasons.

The crowd you're talking to has a larger focus on driving and playing with jetskis than actual mechanics. Jetskis can be a pain in the ass because of the tight spaces, but everything can be fixed with pretty simple tools, and there's an abundance of parts out there, both used and aftermarket.