The colleges I am applying to use the superscore.
However, should I send in both scores or just one of them?
1st time -
1400 (730 math / 670 reading)
18/24 on essay
2nd time -
1500 (790 math / 710 reading)
17/24 on essay
I would send the 1500 only as that sitting places you in the best light. I don’t see a difference between the 18 and 17 on the essay to merit sending in the first sitting scores.
@ThinkOn thank you 
also this may be a dumb question but I also took the Math II subject test twice and got a 670, then an 800. Do you think I should send the 670 to show that I improved?
No. Colleges won’t care. It’s a given that most students will improve their scores on a retake.
No, I would just send in the 800. For the top schools, I don’t think anything starting with a 6 is something you want to show the AO when you have a much much higher score.