We sail/race SF Bay. The water temp outside the GGate is in the low 50's even in summer. Inside the bay, the windy and deeper parts peak
in the low-60's in summer, falling to mid-50's other times. There are estuaries with summer highs from 66 to 71, but not for real sailing.
This hypothermia table
shows how long you survive under certain conditions. Given the 25kt winds you were probably sailing in when you went in, which exacerbate the cooling, you have 15-30 mins before you are unable to assist in your rescue and have to hope there's a block and tackle and experienced crew at hand. You will be unresponsive, depending on wind, in about an hour - 2 if you're lucky.
An older sailor told me the best man overboard policy is "if you fall in, you're dead". Kinda gets your attention. Also, I've had some experiences...
Anything you can do to not thrash around, to huddle up and try to keep still water next to your body, will add valuable minutes. Wearing a wet or survival suit makes the most sense, and will add a lot of survival time, but someone still has to get you into the boat. Ladders rarely work because they don't go deep enough into the water for people's feet to reach, and because they'll be too exhausted.
I wear my life vest almost
all the time (cruising to the fuel or haulout dock on a calm day, maybe not). But the real issue is: how are you getting out of the water? You can run "idiot lines" (loose hanging scalloped ropes tied to cleats on deck sides), and I've done that, but I've also fouled a prop with them (knotty problem). If someone goes in, I'll rely first on tossing a preserver, then the Life Sling to get them out. But I might also run a line from a mid-ship cleat to a winch, slacken it into the water and have the man overboard get their body onto the rope so I can winch them partway up, at least get them mostly out of the water so we can pull them up or use the Life Sling block and tackle.
The lifejacket is almost a moot point in our waters because it won't stop the hypothermia. Serious racers wear suits & that matters, but the real discussion is about getting out of the water.
I have 30+ years of water skiing, windsurfing, kayaking, and lake sailing which have taught me about hypothermia, but only 4 yrs on keelboat, so I'm open to suggestions, now, before it matters.