I have no idea who Sylux really is because I have never played Metroid Hunters, what can he do, and what would pursue me from wanting to support Sylux over Anthony Higgs?
Not a lot is really known about Sylux, really. Part of its appeal comes from the mysterious air it gives off, at least to a lot of people. Basically, its gender and species is unknown, but what
is fact is that it harbors extreme hatred towards the Federation, and Samus by affiliation. Although by going off of the fact that its tracking her at end of Prime 3, it could be more than just that.
Sylux uses stolen Federation prototypes for its weapons, powered armor, and I think its ship, the Delano 7, as well. Sylux also has its own alt-mode. Similar to Samus' Morph Ball mode, except that it hovers around instead, traveling very fast, and can lay down trip-mine bombs. If it links two, you have a standard trip-mine, but if you form a triangle around an enemy with it, it'll close in on them and cause massive damage, usually resulting in an instant kill in
Hunters' multiplayer. The bombs can also be detonated in rapid succession to give the Lockjaw mode a sort of limited flight capability (though it's more of like an extended glide). Its trademark weapon is the Shock Coil, which uses weaponized neutrinos to create a pretty much electrical stream that drains a target of energy, and refills Sylux's own energy in the process.
Another thing that made Sylux stand above the rest in
Hunters was its boss fight. Sylux has pretty cool theme music, sure, but the real kicker was that you also get to fight the Delano 7 while coping with Sylux itself at the same time. So really, it was cool to fight another bounty hunter that could actually prove a credible threat to Samus, which is saying something. Samus is in a league of her own, and the only group that can keep up with her were the Hunters in Prime 3, and Prime Hunters' cast as well.
So in short, it had a cool boss fight, music, has a history with the Federation and presumably Samus, has a killer alt-mode, an interesting weapon, a ship, and now, seems to be an up-and-coming antagonist, and could provide a more unique moveset since it could use the various other Hunter weapons including it's own. I mean, if its taking after Trace for one of its moves, it actually would have a legitimate sniper rifle LASER.
Hunters is so far the only game to have a sniper weapon that you can use, and man, it was scary powerful!