Although the same emitters (SST-40 6500k or 5000k), they’re different lights to a significant degree. They both put out a ton of light, the edge going to the SP35 if for nothing else it’s larger diameter and deeper reflector. 21700 cells provide more capacity/run time. ATR (Advanced Temperature Regulation) is non-adjustable and built into the driver/firmware. Good info here:
SP35
SC31 Pro runs Anduril firmware, temperature regulation is user programmable.
SC31 Pro
Sofirn now makes a magnetic tailcap as an accessory for both lights.
I prefer my SC31 Pro’s, both in 5000k. One set up with the magnetic tail cap and 18350 short tube for knocking around in the summer, just dropped in shorts pocket. My SP35 is the 6500k ATR version. Wall of light, and a little better reach than the SC31, but I just can’t warm up to it. The beam has annoying artifacts, I don’t like the switch or the UI, and the scalloped tail cap is sharp and uncomfortable in hand. Might order a mag cap to swap out and see if I like it better.
Just my thoughts, whether or not it answers your questions.