This is a hard choice and there is no wrong answer. You have done very very well! A scholarship from a top 10 is a big achievement!
I can comment on connecting with people at Yale vs. Sloan. I had it both ways in jobs and BSchool classes. It is definitely a better start if you start out with a sense of connection but I found that it is a minor readjustment as I had to figure out who I was clicking more with and how to fit in. Will take a few weeks to discover all of the great and horrible people in both programs...
Being a rankings whore that I am, I can't resist pointing out that Sloan has been ranked #4 by US News in the latest round. I don't know that it is on par with Stanford and/or Kellogg but may as well ride the high wave while it lasts and with your long term goal being what it is, perhaps you can cut through the crap and get to it faster (not sure if you want to be doing a startup with a bunch of bschool student debt but not unheard of). Having more people who are like-minded will stimulate and push you (and scare you too, which is helpful). You may realize that is not what you want to do eventually as you see everyone going into tech and startup mode what price it comes at. Could save you 10 years.... or accelerate you and save 20.
If you are going into Tech, MIT is a sexy name to have on the resume and while you went to the shiny BSchool instead of the underground math and physics labs, you will still share some of that cache.
P.S. At the same time, starting a business with 70K pays for a year's worth of living expenses. Had you been looking to start your business right after bschool, I would probably suggest weighing Yale more due to the financials. No wrong choices unfortunately