Being realistic, unless you are talking budget brake lever/shifter combos. the format is dead.

Shimano hasn't made MTB STI's since the ill-fated DCL's, and SRAM never has.

What you do get now is matchmakers/I-Spec, which allow you to use the same clamp for the brake lever & shifter, some aftermarket brands even produce their own to allow aftermarket brakes with SRAM/Shimano shifters.

For which to choose between SRAM & Shimano, this is governed by your derailleurs, as normally these need to match the shifters.