As Arizoney said, I believe that it's whatever feels more natural to the player.
Omaha has always been my first game and feels very instinctive to me, whereas Holdem, I have to work at.
Remember that Omaha is a drawing game, not a "made hand" game, so strong draws to the nuts are often favored over, for example, a set on the flop.
Also, remember not to overplay your pocket pairs. There is no such hand as AA in Omaha. HE players tend to way overrate any pocket pair.
Here are a few threads to look at. Maybe one day I'll write my own.