So if I understand correctly, you're pretty new to diving with 15 dives, you're in California and I'm guessing interested in (shore?) diving locally, and you've got a dry suit & some sort of Air2.
I've never shore dove in California. I do use an Air2, and I prefer steel tanks for offering me more air. If I were in California talking with you guys about going on a shore dive as a trio, and hearing what you've said to each other, I think I'd comment like this:
1.) I use an Air2, but my primary reg. (an Atomic B2, hoses as they came from the factory) has a fairly short hose between 1'rst & 2'nd stage. So if I donate you my primary in an OOA, we're going to face-to-face, real close. If we were planning to shore dive somewhere with substantial waves & surge that make exiting something of a challenge, a traditional octo. might offer an edge (of course, the tec. inspired people with long hose setups, donate your primary, would have it even better, but I have no experience with that).
2.) I've never even worn a dry suit. I know they introduce a 'new' airspace to deal with and can complicate buoyancy management and until you get it down. Adds a bit of task loading, I'm thinking. You've only got 15 dives. You might be quite proficient with a dry suit, please take no offense, but I'd at least be somewhat worried.
I could argue with some of his other input, but others here have already done that effectively, so why beat a dead horse?
Is this guy really trying to dictate terms, or is he just a Type A personality who's unconsciously more forceful/overbearing with his opinions than he ought to be, and trying to 'help you for your own good?'
The former I'd probably avoid, but the latter you might could work with. But you may have to exercise polite assertiveness, since it sounds like he'll tell you what to do if you let him.
Richard.