They’re almost opposite.
Common points: strong academics and cold weather (colder for Macalester, but Colgate isn’t balmy most of the year either.)
Macalester is urban in one of the best city neighborhoods with close access to public transportation and many company headquarters, Colgate is very rural and isolated, with a lot going on on campus.
Macalester has less drinking/partying (in part due to location: rather than partying together, many students head into the cities), Colgate has a vigorous Greek life with lots of drinking/partying on weekends.
Macalester’s athletic teams aren’t anything to write home about although supported by friends, more insistence on all student participating regardless of skill; Colgate has Div 1 sports and a sports culture.
Macalester is relatively liberal, Colgate is relatively conservative (keeping in mind young people are usually more liberal overall than older people)
Perhaps post on each college’s subforum, so that alumni write back with their impressions. In addition, ask Admissions at each college to get you in touch with current students in STEM and in Spanish. Ask them what they like best and least about their college, (to see if you could live with the “least”), who their favorite professors are and why, what people typically do on Friday night, etc.
Personally, I’d pick Macalester just for the neighborhood, it’s fantastic living there, so many opportunities to interact with different people, access to everything… while still having a real, compact, well-defined campus. But… that’s me and I’m not you In reality, there’s no wrong choice! It all comes down to personal preference.