I personally think that KF has much better mechanics than VoG, but all the year one players want to pick VoG because they can take pride in being the first to step into it. It's loot was arguably worse than KF because if you were missing even one piece (which a lot of people were), you were stuck doing a ton less damage than the lvl 30s, whereas 315 vs. 320 is not too significant in damage difference. Sure it was big and gave a sense of plunging deeper and deeper into Venus, but most of it was empty space with nothing important.
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KF still is my favourite. Vault always gave me utter garbage loot drops, and it got pretty boring towards the end of year one. Do t get me wrong, it's visually stunning still, and I think the transitions between fights were better than KF, but I like that KF punishes passengers and mistakes harder than the other two raids. Feels heaps better when you nail the bosses in a couple of rounds