We have the Crewsaver Ergofit 290 oc's & wore them for around 400 nm last year at Oban & then throughout the summer. Very comfy, tbh you don't know you you're wearing them. We wear drysuits pretty much all the time when we're out, unless it's exceptionally warm & sunny. We've not had cause to try & swim in the lifejackets yet, but I suspect that's a moot point. I carry PLB/rescue laser/knife/Handheld about my person when underway. We got the lifejackets at the 2013 London Boat show direct from the Crewsaver Rep on the Andark stand, we were playing him off against the Spinlock guys on their stand, we tried both jackets on & there wasn't much between them, when it came to the "deal" the Crewsaver guy won hands down, a big chunk off the RRP, & he chucked in:- re-arming kits, line cutters, twin elasticated lanyards, storage bag... it was getting embarrassing even for a Yorkshireman
Spend time setting them up & adjusting them & they should be comfortable.