Would you prefer a research job at a BB or an IB job at a boutique?

depends..is it a well known boutique?

if you're starting out your career and don't have a preference/passion for one career over the other, then take the big name. it gives you a bigger alumni network, better marketability/visibilty when throwing your resume around, etc.

i.e. Morgan Stanley Research vs Morgan Something or other banking

I had the same choice and obviously I took the boutique. But I wanted to do banking and if that's really what you want, then go for it.

From my perspective, it's simply a lifestyle choice. I view both essentially as apprenticeships prior to doing something better/greater, and whilst IB probably offers marginally better exit opportunities, research doesn't steal your girlfriend in the process.

Agreed, go for IBD and don't look back. You can always go to ER if it doens't work out, but the reverse is not true. The IBD exit is also much better and even better for MBA.

How about research BB vs. capital markets BB? I've always wondered about this one.

It depends, even BB E.R will not get you into PE. If your route is more to stay in ER or perhaps a HF, then yes. But if you want a vast span of exit ops, IBD at boutique would still get you where you need to go.