Yeah, planet size truly matters, in that anything less than the largest option is likely to be too small to approximate old terra.
I wish there were different presets for the world conflict, so it could be more man vs nature than factions versus factions, if you lived on a planet of monsters. That would make an interesting co-op between human players. If we get naval stuff, just imagine playing on a water world with huge Lovecraftian sea monsters that can eat entire installations.
I'd like to see more victory options too, such as building a quantum transreceiver thingy to summon the Shadow on the planet or building a warp ship to recontact the rest of the galaxy. Then other players could nuke your building site before you are finished, just because they are dicks like that.
Largest size is also important, plus generating a small colonization population. You can also see how many zones were colonized and compare to total zones that was given in an earlier step of planet generation. It's all about just rerolling for each stage until you get what you want. Go Hydra if you want more monsters, otherwise you're more likely to be fighting Free Folk Marauders. Cerberus also seems to produce rock monsters. Hopefully, the planet generation will someday allow more fixing of settings so its less reroll based.
Frankly, most worlds my people have been trapped on are so horrible that just building a warp ship and leaving would be truer victory than conquering the hellscape. Most generated worlds aren't worth fighting over from a terran survival standpoint, except for the fact you're trapped there and can't leave.