Having done high school in the US, bachelors in the UK, and coming back for MFE in the US this year (also having applied to both of these), I might be able to offer some good insight for you.
Career wise, if you're an international student in both countries, it will likely be easier to land an offer in the UK (still much harder than for locals unfortunately).
1) the UK offers a "graduate visa" for 2 years with full time work allowance upon graduation (assuming you haven't used this already).
2) there's less hoops to jump through with sponsorship compared to the US if that's the route you'd need to through.
Academically, the two programs differ a bit and it kind of boils down to your ideal time frame for completion and what kind of quant finance you'd like to do.
- Imperial is 10 months, Tandon is 2 years (though 25% of students choose to complete in 1.5 years). If you don't have any quant work experience, it might be worth it to slow it down rather than rushing through and that being the problem for full time employment.
- If it's a true quant role you want, this Imperial degree is said to be a bit diluted by the risk management component vs pure quant, so more tailored to traditional finance. Look up "Imperial RMFE" in the search bar on here and check out a few threads, generally mixed reviews. Tandon has a bit more variety with how you want to tailor your experience with a wide range of electives and 4 different study tracks, so you have more discretion there. I think they are computational finance, risk, corporate finance, and tech/algo.
As a side note one thing that worries me is when I look up current students at Tandon (class of 2025) on LinkedIn, most have not secured summer internships. Don't know if it's on them for applying too late, on the tough job market right now, or on Tandon. Haven't done research on Imperial RMFE to compare this.