What to do for a senior spring internship?

I'm a senior graduating this December and I want to do something this spring to get some experience and earn some extra cash before I start my job. I'll be recruiting for full time analyst positions this fall, and I was thinking that if I could get a spring internship offer and accept it this summer then I would be more competitive because I would have the expectation of being more experienced.

Would getting such an offer really be helpful in full time recruiting? And what kind of internship should I pursue? Most investment banks don't offer spring internships, and if they do then they seem to be part-time internships oriented towards students. I'm looking for something full-time. I'm planning to contact either regional boutique investment banks or small private equity funds to see if they could use a full time intern. What do you think is the right choice?