SAT Math I vs II

CC newby here.

Is it preferable to submit an SAT Math II score of 780 or an SAT Math I score of 800?

Send both. You won’t be penalized for sending an extra test score.

I believe you’re only allowed to send one

Incorrect. You can send all your test scores. They will look at the ones that put you in the best light. Anyway the difference in scores is negligible. They both show that you can handle the rigorous coursework that you will encounter at MIT, which is the only reason they require these exams in the first place.
I guarantee that if admissions loves everything about your application, they won’t disqualify you because you sent in an extra math score.

@UglyMom This year’s MIT Application only allows one to report a sole Math SAT 2 and a sole science SAT 2. Hence, even if the OP wanted to report both Math scores, they would only be allowed to report one.

@Fibbonachi10 Just because there is only one spot to self report doesn’t mean you are not allowed to send more than one in, nor does that mean that MIT won’t consider any other scores if they see them,
For example, If you fill out the application for EA by Nov 1 and report/submit a physics test score, but then take the SAT subject test again on November 4th,tell admissions that you are taking it again, and have the scores sent directly to MIT, they will look at and consider this second test score, as long as it’s better than the one previously self reported. In addition, they would accept scores from a December test if the student ended up being deferred. They even used to accept the scores from tests in late January for RD applications due January 1st, but the College Board did away with that exam.
Many times MIT has said that they will look at the scores that put you in your best light. This is not something I see MIT changing their mind about.
@MITChris, there were a few very helpful people giving reliable advice for MIT on CC when my daughter was applying. I’d like to pay it forward, and contribute where I can. Please correct this info if anything has changed. I don’t want to be giving out incorrect information. Thanks!

@UglyMom Fair point. I wasn’t stating that the OP cannot send other scores or that other scores won’t be considered. I was only referring to self reporting.