Developer here. Sorry about that. I really do need to make a web site.
So far, Retro has been oriented toward the several dozen active competitive pilots out there. There are so few of us; we know and see each other regularly. When someone wants to know the difference between Retro and Rebirth, they just ask me. Actually, anymore what they say to each other is, "Just get Retro". ;)
I, uh, haven't really been thinking about new players.
The differences between Rebirth and Retro in a single player game are slight; Retro is mostly oriented toward fixing pain points in competitive multiplayer. That being said, there are a few differences.
Homers and smart missiles in Retro use the game's original algorithm for tracking, while those in Rebirth use something different. So both your missiles and the superhulk's missiles will behave differently in the two versions. Rebirth homers are better at going around corners, and while they're easier to dodge the first time, they're harder to ultimately lose. If you like to dodge homers in an open room on the higher difficulties, that's where you'll see a difference.
Homers in D1 Rebirth track proxies over robots / pilots. This is accidental D2 code contaimination, and has been removed in Retro. You'll notice this in levels where the robots lay proxies -- it was a particular problem for me on level 20, back when I was playing a lot of Rebirth.
Retro has dug a couple bugs out of the collision code, one of which was introduced by Rebirth, and one of which goes back to the original game release. If you like to make ninja close dodges, especially with homers, Retro performs the same every time; Rebirth will sometimes clip you with something that you actually dodged.
Other than that, it's little HUD chrome things. Retro has shield, energy, and ammo warnings. I like them in single player, but traditionalists generally don't.
Anyway -- Rebirth isn't a bad choice for single player. I've said in the past that the Rebirth community is more focused on single player and coop, while Retro is for hardcore competitive anarchy. That is okay with me. :)
So far, Retro has been oriented toward the several dozen active competitive pilots out there. There are so few of us; we know and see each other regularly. When someone wants to know the difference between Retro and Rebirth, they just ask me. Actually, anymore what they say to each other is, "Just get Retro". ;)
I, uh, haven't really been thinking about new players.
The differences between Rebirth and Retro in a single player game are slight; Retro is mostly oriented toward fixing pain points in competitive multiplayer. That being said, there are a few differences.
Homers and smart missiles in Retro use the game's original algorithm for tracking, while those in Rebirth use something different. So both your missiles and the superhulk's missiles will behave differently in the two versions. Rebirth homers are better at going around corners, and while they're easier to dodge the first time, they're harder to ultimately lose. If you like to dodge homers in an open room on the higher difficulties, that's where you'll see a difference.
Homers in D1 Rebirth track proxies over robots / pilots. This is accidental D2 code contaimination, and has been removed in Retro. You'll notice this in levels where the robots lay proxies -- it was a particular problem for me on level 20, back when I was playing a lot of Rebirth.
Retro has dug a couple bugs out of the collision code, one of which was introduced by Rebirth, and one of which goes back to the original game release. If you like to make ninja close dodges, especially with homers, Retro performs the same every time; Rebirth will sometimes clip you with something that you actually dodged.
Other than that, it's little HUD chrome things. Retro has shield, energy, and ammo warnings. I like them in single player, but traditionalists generally don't.
Anyway -- Rebirth isn't a bad choice for single player. I've said in the past that the Rebirth community is more focused on single player and coop, while Retro is for hardcore competitive anarchy. That is okay with me. :)