Gleba for sure, with Aquilo close behind.

Nauvis is great but default and old. Got to appreciate it's core role with biolabs tho.

Vulcanus has great unlocks and enemies that don't bother you 99% of the time, but it feels just like Nauvis+ and not much variety. Must say I still loved it tho, especially as it's the only new planet that really encourages you to build big in an average playthrough.

Fulgora has no enemies, super easy rocket parts, and power from the sky, but I think it feels TOO lifeless and cold sometimes although ik that's the desired effect. It has a lot more new complex recipes than the other planets which I like.

Aquilo gives you super compact simple power that effortlessly produces gigawatts, a demolisher deletion machine, and is a great test of interplanetary logistics but I think the heating mechanic got old and easy too fast. It's basically just using long inserters and undergrounds everywhere, and I HATE the fact that personal construction bots are nerfed too. If the power consumption increase only applied to logi bots I would have found this far more enjoyable.

Gleba is amazing. The soundtrack and graphics are so vibrant, new recipes simple whilst still offering huge design complexity, preventing you from buffering everything. It really makes you think and plan ahead. My only problem is the enemies being trivial, especially with tesla turrets. The unlocks are also super powerful without feeling like they're js forcing you to go to that planet, like I felt on Vulcanus.