EDIT: Just realized you were talking planet. Reading comprehension is poor these days. I suppose if I had to choose, it'd probably be Pygar for it's unique landing animation.
I do love me some Planet Erie. Moreso before the planet became Red Faction: Guerrilla. It had an interesting domestic situation and tension with the split governance, seemed a much nicer place to live on average than your typical Sirian hangout, but still had an air of danger with the vicious wildlife and frontiersiness of it. All pretty cool next to turbopoverty / megarich split and corporatism right next door. Like Orleans in Gallia, but less boring.
Alas, story beats come for us all. I guess my runner up would be Jiangxi for the thinly veiled STALKER references.
Leeds (It's probably my favourite planet because it used to be the most visited and vibey place in both the vanilla campaign and older versions of Discovery)
Gaia
Toledo
Toulouse
Nuremberg
New London
California Minor
Cambridge
Gran Canaria
Kyushu
Pittsburgh
Kurile
Harris
New Berlin
Crete
Sprague
Pygar
Weimar
Akabat
Tomioka
Marne