I would not buy anything that requires 'pulling a tab' if you are in an open boat. During a power boat crash, you are being flung so violently, you'll never have the opportunity to pull a tab, much less find it.
If you get bumped on the head while falling overboard, and knocked loopy for a few seconds, the pull tab jacket will be worthless.
If the boat is going to be running 75 plus, you should definitely think about getting a jacket with "impact" material. It should also have leg straps to keep the jacket from pulling over your head, and material strength should be 100mph rated.
I've been in three crashes, and believe me, they happen too fast to be able to mess with tabs. I've also been knocked into the water and momentarialy stunned - twice - so I'd never give up my race jacket which is designed to keep my head turned up and afloat. When your arms or legs are injured, you can't roll yourself over too well. And when you are knocked out or have the wind knocked out of you, it's impossible.
Don't worry about Coast Guard ratings. Just keep some $10.00 pfds on board, and you'll be in compliance with the CG laws. As long as they are within reach in the boat, you're ok.