Should I take the ACT again?

I took the ACT for the first time (it is not very popular in my area) and scored a 31 with barely any prep. My biggest constraint was time, I had to guess on about 3-5 questions on the Reading and science sections. I’ve mostly been focusing on the SAT. Though I received a 1390 on my first SAT attempt (with no prep), I have been prepping seriously and I am currently awaiting a score, which I hope to be at least 1500. I am currently studying to take the SAT again, so is it worth it to take the ACT again in my situation? Or should I just stick to the SAT?My first choice school is UPenn. Although my score is in UPenn’s range, it is on the low end so I would be shooting for a 33+ for my next score. If I was to take it again, I would also do the essay. Thanks.

@AnthonyZ I would take it again especially if you scored a 31 with hardly any prep.