I primarily play hold'em and haven't done much with PLO aside from study it a bit and play a limited number of hands so my opinion may be slightly biased. I do however feel like omaha is more complex and it seems a bit more difficult to grasp onto the subtle parts of the game comapred to NLHE or LHE. For a beginner it is probably best to learn NLHE before PLO as alot of the basic concepts you need for PLO will be learned playing NLHE. So starting PLO from scratch would probably be much more difficult...

Hope that helps. Maybe some omaha players will respond here and give their 2c.