No one can decide for you. For a start, you might have really short legs or something. Or perhaps your knees are at different heights.
But that aside, longer cranks give more torque, and shorter cranks give more speed. More speed = more momentum which means less need for torque in many but not all situations.
With long cranks (150mm plus) a few mm difference makes little real difference because the % change is small. With short cranks (140mm or smaller) even a few mm can make a significant difference.
Personally, and it’s only me, I’d say 150s are a good general purpose size. fast enough for the flat, quick enough to ‘rush’ obstacles, and with enough control to idle and revers easily. If you want to plod up steep hills or drop down deep dark dirty gullies in search of Aardvarks, then longer cranks can’t hurt.
I’ve been using 170’s for awhile now. I’ve also been going through a lot of cranks. Anyway, I thought the last pair I had on were 170’s too, until I noticed they were 165’s when I was taking them off. I hadn’t even noticed they were different. Now I have 175’s on, because they are the last set of cranks I have. I did notice the difference between 165 and 175.