They're both a bit big, are you sure that a 35' casn take these without tipping or sinking or busting davits?
The jet rib will be miles more practical. The jetski will be even more of a laugh, but only for the first day, and not much use for getting loads of people ashore and possibly banned in certain areas if not now then soon.
I agree with Matt, the RIB will also be more stable for getting in/out of and if the bathing platform is as big as on the Doral 360se on their website I expect it will sit on that quite easily
A small Rib with outboard would be cheaper, depending on engine not far away from being as fast and the most practical of the lot.
If you get a Jet rib you will need a crane to get it in situe on the bathing platform and the inboard engine takes up a lot of room in what is already pretty small.
You really should not countenance a jetski as a tender. They may be fun for ten minutes until the novelty wears off but as a means of transporting people and things to and from the boat dry, they are just non starters. Do you really want to kit up in your wetsuit just to go ashore?
Having seen an Avon Jetrib in action that would be the one I would choose. It was as quick as a jetski and has nearly all the manoverability including neck stapping 40knt 180 degree turns on the spot - plus all the other benefits mentioned by everyone else. PS Can I borrow it?