Way too many variables to answer x or y. Ive been on a boat that sunk on the home stretch of a 7month ocean crossing - one thing that no one has mentioned here is the mental state you may find yourself in. Some people react calmly, others panic, and you cannot tell who is going to do which one until it happens. The people I thought would be mentally together turned into flailing balls of panic (Yep, think that scene from the flying nun...now put a cool bodybuilder type dude running round the mast screaming in that scenario..yep, we had to physically pry him off the mast and throw him overboard..a fist fight on a sinking boat is not a good situation and one that took valuable time and added a whole new level of stress to the situation). The question in the OP assumes a scenario where you are not confronted by things being thrown around everywhere in a boat rapidly taking on water...your dive gear may be stacked on deck nicely but once the boat is not level and water is flowing around id love to see someone manage to find their gear and calmly gear up and slip into the water. When the decks under water your freediving skills to get your gear and put it on best be fantastic...i couldnt manage it. Shaka Doug is correct, no two boats sink alike.
Imagine you are on a liveaboard on the second deck and you are awoken by crunch, alarms, thuds, crashes, water gushing down the companionways bringing assorted debris with it. That debris can be something as simple as a can of baked beans which split my eyebrow open as it hit me. So you are in darkness, trying to work out wtf is going on, trying to get up out of your cabin and on deck - dont assume others are going to politely move out of the way to let you get past them.
What we plan we would do in a situation is often totally impossible or totally forgotten about in those moments. The yacht I was on actually took quite a while to sink, the process leading up to the boat slipping beneath the surface can be seconds..minutes..or in my case..an hour. That hour still did not give me time to get anything other than a life jacket on before having to swim for it. Most of that hour was taken up with dealing with other people freaking out, setting off Epirbs, cutting lanyards where needed and trying to get as close to land as possible.
Until you have been on a boat that is sinking, its all just hypothetical.
Personally...id do everything exactly the same. It wasnt pleasant going into the sea at 4am in october in a storm in jeans and a jumper but I did have a life vest on and could see land which we all made it to. The outcome of that sinking if it had been a couple of weeks before halfway between thailand and australia's west coast would have been terribly different.