Hold'em is certainly a simpler game and there will be many, many more times/places to play. For me, Omaha just adds some variety. There are two variants of Omaha - High (often simply referred to as Omaha), and High/Low (or OMHL). OMHL seems to attract more beginners since it 'seems' easy to play the low hand, while it is clearly more difficult to play the high, or ultimately the high and the low
hands at the same time. You often see low winners losing money as they end up splitting the low half of the pot while the high winner gets the full share of the other half of the pot. This is probably where beginners have the most difficulty. You see them aggressively chasing the low hand (often still a draw) without a good high hand at all.