LSAC GPA vs Cumulative GPA for pass/fail question

For context, I transferred from a state school to the University of Southern California as a sophomore, and I am a business major, international relations minor. Most classes at USC are 4 units, but at my previous school they were 3 for some reason. This semester I got 3 As (4 unit classes), an A- (2 unit class), and a B in a 4 unit class. We have the option to do pass/fail and I am deciding whether or not to use it for the B. I used https://7sage.com/gpa-calculator/ to calculate my LSAC GPA, taking A+s from my state school into account even for easy classes, and when I take away the B (pass/fail) my GPA goes up a lot to a 3.86 from a 3.82. When I use a cumulative calculator that does not take A+s into account since USC doesn’t have A+ but my old school does, my GPA goes down when I do pass/fail (meaning the B would help me). How accurate is that LSAC calculator? Meaning, should I base my decision off of that LSAC calculator or my cumulative GPA. Also, people keep saying if I do pass/fail law schools might think I got a C- (minimum to pass) which would look worse. I am so confused what to do and would appreciate any advice.