L1 and ONML voteoffs are over, I can reveal my speculations without affecting the results at all. I thought that "No added colours or lemmings" was the biggest front runner in L1 voteoff "It's hero time!" behind it, but during the voteoff I started to ponder if "It's hero time!" would actually be the winner due to multiple solutions nature.
"This Corrosion" was the clear front runner in ONML voteoff, I predicted that that would have won it. At the beginning of the voteoff, the only levels I could think of challenging "This Corrosion" were "ROCKY VI" and "There's madness in the method". Quite a rise from Havoc 5 all the way to the victory in the end.
Aaaaand here's the topic that gave most hints for my predictions. This linked post even collected the previous data from the topic.
EDIT: Oh yeah, and my favourite levels were "No added colours or lemmings" and "This Corrosion", I voted for those every round. My taste hasn't been influenced by Lemmings forums, those two levels were my favourites already over 10 years ago, and when discovering this community, I was happy to notice that other people respected those levels too!