I don't have any experience diving NorCal, but from what I've read I get the impression that most divers use something smaller than 110. The visibility is generally poor so that a smaller gun is all that is needed, and the fish are either small or just sitting on a rock waiting to be speared (ling cod).
In SoCal a longer gun would be better, but you can certainly take large fish if the visibility is poor and/or you get close enough. My avatar shows a 30 pound white sea bass I took a couple of weeks ago, and that gun in the photo is an Abellan 110. And under kelp paddies floating offshore, yellowtail can be almost suicidal for the first diver in the water, and can easily be taken with a 110.
If you want to maximize your chances of landing big fish, you might want to consider using a threaded shaft with a slip tip. Mori's slip tips are considered the standard, and Sea Sniper, located in Santa Cruz, has a very nice new tip that I used on that fish in the avatar.
If your shooting line is attached the muzzle of the gun, then you are going to have to install a reel or use a breakaway float line for large fish. Each choice has its advantages and disadvantages but they keep you from having your gun taken away from you. For instance, that little 30 pound fish in my avatar went straight to the 50 foot bottom in spite of my best efforts trying to stop it. I would have lost the gun if the shooting line had been attached to it. Forgive me if you already know all that, but since you didn't mention a reel or float line I thought I should bring it up.
I'll be glad to try to answer any questions you have about SoCal.