Throw in Hidden Machine, which provides a V2 boost that Gamma builds have no access to with the Hunter tree, and the Power Inside,
Hunter’s Eye Armor Damage vs. Robots is V2, and quite a hefty one at that. It is, of course, limited in its usage. The thing here is that getting Hidden Machine for a V2 type boost does not end up mattering that much because of the tradeoffs involved in going for such a setup. Getting this new multiplier by losing a significant amount of stuff somewhere else results in it being not as powerful as it could be.
Also, the fact Gamma Anoint does get an increase from Weapon Type Damage boosts means you can get V2 from your Class mod + Artifact.
Gun Damage
Gamma is a setup that likes getting extra Gun Damage, since it does not get any of those absurd 100%+ increases from anointments. Green + Blue gets a good amount of it, but still benefits from increasing it. Red + Blue, however, does not get as much Gun Damage from its combination, and is rather a bit more concentrated on V1 and Crit. This means it will absolutely love Gun Damage increases, and you can also find that on a Class Mod. The newly introduced Pearl also has a massive Gun Damage increase after it’s fully stacked, and it is more beneficial formula wise to Red + Blue than Green + Blue.
Math
On a 1:1 comparison for final damage multiplier on both crit/bodyshot, using just skills + Gamma Anoint (and a baseline value for Grank Crit + Gun Damage):
- Green + Blue has an actual decent edge over Red + Blue right now.
- I made comparisons with all variations of Hunter’s Eye (Off, Human, Bot, Boss). When Hunter’s Eye was on, Red + Blue outpaced Green + Blue a bit vs. Humans, a good amount vs. Bots and by a decently large margin when bossing with a BH.
Of course, this is not an end-all be-all for the question due to the intense variations that will happen in stat rolls and other things. However, when such variations are introduced i’d say Red + Blue is the one getting the most out of them.
Example: on paper, crit is a hefty boost for the Green Setup, but now we must start to think about practicality. Crit may be sigificant to that setup, but it is just as significant for Red + Blue because 1. It is not overstacked at all from skill boosts, and 2. Megavore exists.
Gameplay Practicality
No Big Game means a very short duration for Frenzy, Furious Attack, Psycho Head (if getting that) and Interplanetary Stalker (if getting that). This gets troublesome and can feel pretty clunky in gameplay. You could remedy this with a Cosmic Stalker COM, but you could use the same COM in the Red + Blue setup. And then again, Red Fang is the main attraction of Gamma to a lot of people.
Then there’s Power Inside: this capstone is weird to use with Gamma Burst, and you probably know why. Gamma Burst’s base duration is 20 seconds. This means you will have no TPI for at least 5 seconds of its uptime. With Persistence Hunter, that time increases to around 15 seconds. With Endurance, 30 seconds.
This is a very big problem for a build that wants max uptime on its ability, because you’ll be losing the 50% from TPI for the majority of Gamma Burst’s duration and that really chunks down your DPS. Not only this, but if you got off a cast while below 100% health, you’re stuck with the 25% boost. You can try to work some cooldown juggling, low duration Gamma build for maximum TPI uptime, yet that would be better done with Red Tree.
Pair this with the Hunt Skill duration + Cooldown problems and you have a setup that will feel very clunky to play sometimes. I’ve played with it a lot, and also went further into some Rakk memes with it. It’s completely playable and enjoyable, i just don’t think it really has anything standing out for it in comparison to Red + Blue, especially when you consider the many Gun, Item and Anoint synergy Megavore has, and the fact some enemies don’t have easy to hit crit spots (or any at all at times).
Of course, it also has its upsides. You’ll will be a bit more bulky, although this doesn’t matter too much if using Red Fang. Being faster helps a good bit. As for Pets, this combo might be good indeed, although i’ll leave that experimentation to you for now 
The effective DPS increase from Megavore is not even taken into account for math (at least as of yet), which just makes it that more menacing when you realize these builds have similar numbers in paper, yet one has Megavore + Hunter’s Eye + Big Game while the other does not.
Final/Other Unrelated Points
I’ve been going back to a full, offensive Gamma Burst setup (with Cosmic Stalker/DE4DEYE) again, but for it to be “worth” it over just switching to Rakk/Fade it would need at least a DPS advantage somewhere (it’s fun either way). I think i might actually be able to give it an edge above Rakk, so that’s cool.
DE4DEYE is something i recommend playing around with on Red/Blue Gamma setups. It checks all the necessary boxes, meaning it gets you V2 from the passive, Gun Damage and Movement Speed from Furryous and then you can look for further stat boosts. Even then, it doesn’t really outdamage Cosmic Stalker overall (which also has an important Frenzy duration boost), but it should feel good and likely get more DPS/Single Shot Damage while the 75% threshold is met.
As for more elaboration on Green + Blue, that setup is better used on Fade (in theory). The Fade crit damage makes up for the lack of a big crit formula boost by straight up adding a 2.75 to it. SSpyR and i had a full Green/Blue Sniper Fade Away setup back in October for Mayhem 3 that went around for a while. It fully works on Mayhem 4, it just runs into those same cooldown issues, and by consequence anointment upkeep. Proper Amp Shield usage and smart gameplay was very rewarding though, and makes anointments not as important.
All of these issues for any of these builds get way more pronounced in the Takedown, but you can always play around them to an extent. Slaughter Arenas feel fine and fun to play on.