Being the HUGE nerd that I am (big suprise, right?), it’s Xen, not Zen. meh.
(Sorry for off-topic, back to the topic)
I voted for Vesper Defense Outpost, because I have no clue as to what that one is from (either MP:H or MP3 at the start, I dunno), and because it’s one of the few non-planet choices.
Vesper is from MP:H.
And thank you for the spelling correction on my choice of planet, haha. I knew it was Xen, not sure why I spelled it wrong. Oh well.
And the Vesper Defense Outpost is pretty freakin awesome. It was one of my favorites in Hunters. Although the storyline sucked, the environments there were amazingly cool.
i dont think the word ‘scary’ is fitting to the crashed frigate… maybe ‘eerie’ or even ‘sad’… the music attributed to the environment so much that it couldnt be scary. it made me think of discovery or something, like on videos of robosubs exploring the Titanic.
and with the B.S.L., i didnt vote for it cause Tallon IV has just as much variety, but with the astounding graphics that it had, i think it was a cooler planet. plus the B.S.L. was too controlled, too Galactic Federation for me…
Aether I think it just feels more alive.
and the crashed frigate is not scary 
level 3 Phazon Mines is scary 
it dark and ereery and has alot of phazon and metroids thats scary the crashed frigate is relaxing and fun to me.
the only world that was slightly scary, imo was dark aether.
i really found the games to just be whats expected from a metroid game…dark metal rooms, dark caves, metroid infested rooms, bright outdoors, pirate infested caves
omgwtf?aether 
tallon IV is best, but zebes and that are really close, the only difference is snow-area and space pirate base, but they both have lava, and even a crashed ship!