Jumping Ship on Credit Suisse SA23 Offer

I have an IB SA23 offer from CS and a summer offer from a boutique that I've worked at for a while now. I really enjoy working at the boutique because of the people and overall atmosphere of the work. It is very likely I'd receive a FT offer from the boutique if I work there this summer. Is the summer experience at CS worth going for? I know I'm not likely to receive a return offer, and the work at the boutique is much more involved / exciting than anything I've heard of from a BB. Given a return offer from CS I'd probably go FT at the boutique anyways. Is my time better spent at the boutique? And, in the future would other firms understand my reasoning for making the decision to bail on the offer after already signing? 

Also curious about your opinions on what sort of workflow CS IB will see towards the end of its life. Will it slow down? Would I even have work to do at the end of the summer?