Here’s what I can say as a Carleton STEM student who briefly considered Tufts.
-“I plan to study computer science or data science or applied math”
Carleton’s computer science department is strong. We don’t have specific data science or applied math programs to my knowledge; I imagine the latter would be an easier thing to zero in on through the (decently flexible) math major. So consider how important Tufts likely having those more specific tracks is to you.
-“I plan on getting my master’s degree after graduating from college. But if I am lucky and get a good job opportunity I’ll probably go for that instead; getting a stable job after college is a high priority for me”
I mean in that regard you can’t really go wrong with either school. I feel like Carleton has a more academic than pre-professional personality, but not exclusively so. And my impression is that, generally, top liberal arts colleges (like Carleton) are thought of as particularly great schools if you plan on pursuing graduate school, and top universities (like Tufts) are thought of as the same if you hope to land great jobs early on. Of course, I don’t think is a strict rule. So again, no wrong answer.
-“I don’t want to go somewhere that is extremely stressful or competitive, but from what I have seen neither of these schools are like that”
I definitely have the impression that neither school is particularly stress culture-y. One of Carleton’s big draws, for me, was its professed emphasis on being “collaborative over competitive”. It certainly can be stressful at times, though, and I imagine the same goes for Tufts.
-“If possible I would like to get some research and/or internship experience during college”
Definitely something you’ll have ample opportunities for at both schools. From what I’ve observed among my friends at similar universities, research during school terms is more prevalent. I mostly hear about Carls doing research over breaks. The advantage at Carleton might be more availability and personalization, but don’t quote me on that. I certainly associate Tufts more strongly with the idea of a “research school”.
Both are great options, so congrats. In particular, both are well-regarded for their undergraduate teaching, so I’m particularly fond of them. 