The good news is that you have lots of options here in the Bay area plus a great environment to learn & practice in a variety of conditions that are probably the best in the USA & rival many in the world.
In case you have not used this web site for resources
Now to your challenge.................I'll disclose = I'm an OCSC member.
I did closely look at a number of places before making the same decision even though I already had a BBC. It was a balance between atmosphere, training attitude, boats & location(bay access + travel time from home). Cost was a factor yet it came down to value vs $$$ spent. I'm still happy with my decision.
The costs you have listed for OCSC could be reduced by 20% if you become a member. ....................which if you are going to charter regularly in order to get water time & build proficiency should be part of your calculations. You can even check out each school/club's charter rates too.......although they can be minimized with sharing charters.
Club Nautique - was my 2nd choice, package approach, clean boats, good trainers, have crewed from there with members & others who have chartered their boats.......plus southern bay location
Tradewinds - they always play the low cost card.............I looked at them too (another east bay option which was my focus) but I would agree with FB regarding fleet quality plus they were very laid back maybe too much when it came to explaining training details. I also considered a great package charter deal they had but passed due to fleet again.
J/World is another very good option in Alameda that was not open when I was choosing.
Cal Sailing is definitely a great option for minimizing costs & learning thru BC.....don't think they go up thru BBC. But you gotta like getting wet 'cause starting with dinghys is one of their primary training steps. Then once you move thru all their levels, you could go to a bigger school/club fleet, demonstrate your skills & get certified in ASA or US Sailing for the appropriate level, then take bareboat with them.
Fleets - yup wide array of choices with each location...............suggest you narrow your list & then stop down to really get a feel for each and the school/club in general. The web certainly helps to gather basic info though.
Yes, OCSC has a Gemini 105 in the fleet............I've had a chance to try it out a couple of times.