Full-Time Dilemma - 2 Offers

This is currently my senior year, and luckily I have been able to find employment already.

During August this year, I was deep in the process for a MM in a satellite city (think Atlanta/Washington/Boston/Chicago). At the time, it looked like my only feasible offer. When I got the call late-August, HR told me that they wanted to change the nature of the offer from full-time to a wintership (with optionality from both parties to extend upon fit/good performance/blah blah). I jumped on it; didn't try to leverage it elsewhere.

About almost a week later (early September), I was told that I advanced to a superday at a BB in a dream city (think NY, SF, LA). I was ecstatic but also very surprised because I didn't expect it. I interviewed first round with them in August, hadn't heard back in close to a month, and 3 emails I followed up with during that time had not been responded to. Nevertheless, I did the superday guilt-free, killed it, and then got the full-time offer (starting July) a couple of days later. I accepted it.

In my mind, I was not acting in bad faith. For purposes of job security, I don't think there's anything wrong with accepting the wintership but then trying to see if I could land something more permanent via full-time when the opportunity materialized organically. At this point, my plan was to do the wintership fully, have 3 months break, and then go on the full-time train.

However, as it's nearing time to leave for the city the winternship is in, I'm getting cold feet. Firstly, the city for the MM...isn't great. The MM also doesn't provide street perks like free dinner after a certain time. Secondly, my relationship with my boyfriend got a little rocky during recruit, but has really been improving and I want to spend as much time with him as possible before working (both job offers are not in our hometown). And thirdly, I recently had a chat with my boyfriend's dad (who is the CEO of a big company) who thinks that doing this winternship is silly, and that there is virtually no point in me going if I don't see a) longevity there and b) values that I identify with that will give me an impetus to work hard.

So my question is: would it be bad to renege (only about 3 weeks away from starting) on my wintership? It's not in a city I plan to ever be working in again, so benefits of local networking wouldn't be very high there. My parents don't think it's a good idea but a) they don't really understand the industry and b) I still think it's extremely bad practice that the MM firm changed the full-time to an internship after having gone through 6 weeks of their process (which makes me really doubt their integrity in general - seems like a place that would dump me given the chance). I feel professionally compelled to at least give it a chance (and quit early if I am really not enjoying it / feel home-sick). Is that just silly of me?

Benefits I see:
- get good practice for full-time later so I can kill it right when I start while the incoming analysts in my class are just warming up
- make some money on the interim (obviously no bonus) as a poor college student
- maintain my "reputation" (although if I quit mid-way I don't think that would be very well received)
- fall back option in case something happens to my full-time offer unexpectedly

Cons I see:
- puts my relationships (SO/friends/family) on pause / strains them unnecessarily
- burns me out earlier before even starting full-time where performance then would really matter
- don't actually make that money after expenses: flying out to the new city, paying for occasional visits from BF, rent, travel, food (the last 3 of which are not costs I have to pay out of my own pocket here)

Thanks!