The Samsung 9100 Pro 8TB wins in 4 out of 6 comparable specs, with 1 tie. Its biggest advantage is Sequential Read (2543% better).
870 EVO 500GB wins in 1 spec (MSRP: 95% better).
Recommendation
Choose 9100 Pro 8TB if you want the best overall performance — especially sequential read.
Choose 870 EVO 500GB if msrp matters more to you.
