RNA requires UV light in order to emerge prebioticly through a Cyanosulfidic Protometabolism which would not have been available miles below the ocean surface on the early earth, There also would not have been a way for these molecules to accumulate in something the size of the ocean, They would have diluted immediately.
This is an interesting question but not appropriate for an opinion poll. We simply don't have conclusive science on whether life formed near thermal vents or else where. We don't even know for sure that RNA was the first form of life/lifelike process.
As to the charge that the ocean is too vast for the thermal vent theory, This is not necessarily true. Crags, Pits, And piles of sand near thermal vents could easily have maintained relatively stagnant pockets of water for long periods of time. As the charge that UV light is necessary to create life (only true in one version of an RNA world hypothesis), There could have been thermal vents in shallower parts of the ocean, Especially during a time when continents and islands were forming.
Even so, The asker seems to know a lot about this (more than I), So I hope they will do good scientific work themself. While I don't think this is an opinion question, I'm glad it was brought up, Because I learned a thing or two!
DNA is too hard to form on its own so you say all life must have been RNA must be first.
Then you try to create a pool of life to create RNA. But guess what? It does not.
Then you cheat and add complex chemicals and very unlikely situations to force RNA to form. Like turning the lights on and off and rapidly changing the temperature.
The irony is that intelligent scientist are trying to life in a laboratory to prove that intelligent design does not exist.
Fact: All evolutionist are in denial that life created itself.