Acording to [this answer][1], at low stack NLH tables a 25-buy-in is enought, while 40 or 50-buy-in is needed for middle and high stack tables.

This don't differs too much from what Jeff Hwang estimate for PLO:

> I think a 30-buy-in bankroll is probably adecuated for a small-stackes
> live game.

and 

> [For higher-stackes-games]. For these types of games, you are probably
> goign to want closer to 40 or 50-buy-ins (if not more).

So there is not a big difference between the bankroll needed for NLH and PLO.

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[Jeff Hwang: "Pot-limit Omaha Poker: The big play strategy"][2]


  [1]: https://poker.stackexchange.com/a/721/7280
  [2]: https://books.google.es/books?id=IfYn3HrWE4sC&printsec=frontcover&dq=Jeff%20Hwang:%20%22Pot-limit%20Omaha%20Poker:%20The%20big%20play%20strategy%22&hl=es&sa=X&ved=0ahUKEwihw4eCgernAhVH-YUKHSosAwMQ6AEIKTAA#v=onepage&q=Jeff%20Hwang%3A%20%22Pot-limit%20Omaha%20Poker%3A%20The%20big%20play%20strategy%22&f=false