This is a tough and complicated decision, because you’re admitted to two top-notch programs (congrats!) but you’re not really all-in for either of these majors.
At CMU, clearly you would not have the option to switch to CS. There are a number of different quant-heavy concentrations within Tepper - I’m guessing that switching concentrations isn’t difficult but I’m not familiar with the nitty gritty of this. Another off-ramp that’s both business and CS adjacent could be the Decision Science major in Dietrich. HOWEVER, I’d be very concerned about combining a desire for flexibility and exploration with a mandate to grind out a challenging degree in three years because of the high cost. That sounds stressful and potentially limiting.
In terms of UMD… I’m confused by this:
Isn’t it CMU where this limitation is more acute? If the need to minimize the number of semesters for financial reasons is driving the push to get out of CMU in three years, why wouldn’t the great financial deal at UMD give you more freedom to take the time you need to explore?
The potential limitation at UMD is that you might not end up liking CS, and it’s not clear whether you’d be able to switch into the business school. This doesn’t sound like a “don’t even ask!” scenario like CMU CS, but not an “open door policy” either. Finding out more about CS alternatives at UMD seems like one of the most important things you can investigate. There is a CS minor, so if you wanted to switch out of the major, you could complete the minor and then major in something else. (And often this can be the best path to a minor, as CS classes at many schools are so over-enrolled that it can be tough to get into them without the preference that being a major confers… but that varies by school and I don’t know what it looks like at UMD in particular.) I’m also curious as to whether a student seeking to switch from one Limited Enrollment Program to another (i.e. CS to Business) would have an advantage, by virtue of opening up a spot in the program they’re leaving.
Overall… if you could afford four years at CMU and the question was “is it worth the money,” that would be one thing; but going in with financial pressure to graduate early front-of-mind seems not worth it to me, especially having to make a decision before even knowing what credits they will grant you. You could easily afford four years at UMD (and if your path turns out to be efficient, you could do a BS/MS or double major in four years rather than getting out as fast as possible). If you hated the “vibe” of UMD, that would be one thing… but you don’t - you find the social aspects appealing. It seems as if your biggest concern is navigating a larger school; but honestly, you will make friends, and faculty will be more than happy to help you if you seek them out. The initial adjustment can be a little more challenging at a larger school, but then it can pay off in terms of the wide range of opportunities and social circles. Plus, your AA means that you’ll be placing out of a number of larger intro-level classes, and getting to smaller, advanced classes more quickly.
So, my opinion is that you should take the fantastic scholarship opportunity at UMD, and plan to spend four years there and milk it for everything it has to offer. Resolve to stick with CS at least far enough to get the minor; by that time you’ll have a better idea what you want to do. (Also, it’s easier to end up in business jobs with a CS degree than vice versa!) At some point, no level of prestige can make up for lacking the time to explore and grow as much as you want to (and besides, UMD CS is plenty prestigious).
So, my answer would be no, Tepper’s prestige isn’t worth it unless you can comfortably allow yourself four years. Graduating early should be a decision that comes much later, not before you even arrive. (My kid who went to Rice found that she was able to graduate early; but she also felt like, at that point, she had “paid her dues” in terms of requirements and lower-division classes, and she didn’t want to pass up the advanced electives that were really the best part of her educational experience.) Time is really the most precious commodity - give yourself the option of the full allotment of time in college. Luckily, your more affordable option is also an enviable admit (and the merit itself - which I assume is a named scholarship - will stay on your resume forever too). My vote is, commit to UMD and don’t look back.