I can only offer a little experience at Abersoch and the IOW, little more on the IOM and nothing at all on the others as i've never been
Abersoch - Only ever been for days out as it's only a 2 hour drive for me, lovely place and obviously got a lot of cash floating around as it's Range rover heaven pulling jetskis/boats in the summer lol, great beach and a real nice feel to the place if heading to the wrong side of trendy soon perhaps?
IOW - spent a week in July there 3 years ago, super laid back place with some lovely beaches, great eateries around Ryde harbour area but as a whole it seemed a very relaxed place even in the height of summer, more of a couples get away from it all or take the kids to the beach type of place rather than a lads holiday though?
IOM - Been a few times now and love the place, the people, and the lack of a speed limited in NSL zones
Again some lovely beaches and awesome scenery, super friendly people and some surprisingly good eateries and drinking holes dotted around, can be expensive to get over there although we've always found accomodation and eating out etc to be very reasonable, didnt find much in the way of nightlife though but to be honest i'm always keen to get up early and grab a lap of the TT course before breakfast