They have the advantage because they chose wisely, thinking about what there up against. The mentality for each side is often played differently, a player playing as a Raider plays with the goal to level up, get gold/faction points and blueprints, Its in the name your in it to Raid. So your goal is so simple it's almost mind numbing if it weren't for the bosses and characters, put aleph in and kill grunts, that's it.
The Antagonist mindset is much more challenging as it requires you to be both merciless and patient. Have you ever thought of being an Antagonist and think I want to get Gold, Blueprint, Factions and Level up through these means...nope. It's much easier to do all that as a Raider. Those that Think of doing Antagonist want one of two this, to get there Antagonist affinity when they level up to get specific cards, (these antags are often the one who choose not to fight) and the other type is the kind that want to actually experience the thrill of a Hunt because hunting unpredictable and potentially powerful raiders beats the mundane A.I....and yes MS is right, it is thrilling once you get a solid feel for it.
If you don't want to die at the hand of an Antag start thinking like an Antagonist and beat them at there own game, You lose cause you think you can never get past the horde to reach an "OverPowered and Unbeatable" Antagonist. This game *IS* challenging but if you want to play
laid back as the "food" ( Rewards) rolls in your mouth then it will remind you of that ever time as you suddenly get an Antag. I'm just saying, you cant have your cake and eat it too.
If I can ask of anything from MS is that when a Raider party has a hard won fight and comes out on top in any mission that they get evalutated differently and receive an Abnormal reward for there very clear troubles. like did you die 30+ times with a skilled Antag and still came out on top, that's a 9.0 right there and what ever new reward they can think of.
....I don't know.