This is just, like, my opinion, man.
I usually think of rap battles in terms of three criterion: quality of lyrics, quality of rhythm, and quality of the BURRRRRRNNNNNN.
I would say MadFLeX wins lyrics, though only narrowly, because his voice is just more bearable to listen to than Gasmasq's, which sounds like some white boy trying to do ghetto grunge or something like that.
Gasmasq handily won in quality of rhythm though, he was always on beat and used better phrasing than MadFLeX. He was masterful while tasteful, showing quality very few have in high speed rap battles like this.
But BURN is where MadFLeX takes the cake. He came out of the gate swinging full on, and it felt like Gasmasq pulled his punches, even at the end he didn't plunge the dagger in like FLeX did. And FLeX didn't just stab; he twisted that thing. Like thirty times.
Sorry Gas. You need better burnination. MadFLeX wins. Supreme victory.