It is not that clear cut from an academic perspective.
It all depends on the relative weighting you assign to research t vs. class size, and which environment you think you are more likely to thrive. If you do well at either school, you will have plenty of opportunities in finance.
Amherst will have smaller class sizes, but BC is ranked 12th in the US for finance research, and 20th for Economics.
Amherst claims to do “high quality research” on their web page, but they are not ranked among the top 25% of Economics institutions in Massachusetts, and they rank 9th among the 11 NESCAC schools for economics research.
For comparison purposes, BC has a Business School and a Phd program in economics and among NESCAC schools, Williams and Tufts have masters programs in Economics while the other schools only have bachelors programs.
US Finance
https://ideas.repec.org/top/top.finecon.html
US Economics
https://ideas.repec.org/top/top.usecondept.html
Massachusetts Economics
https://ideas.repec.org/top/top.usa-ma.html
LAC Economics
https://ideas.repec.org/top/top.uslacecon.html