Straights in Limit and Pot-Limit Omaha
In limit Omaha you will play such situations that even don't consider in pot-limit Omaha. In a limit game you will call raises with more specific hands than in pot-limit game. If you make nuts straight on the flop in Omaha hi-limit, you'll play further, even if flop has two suited cards, while in pot-limit, you will drop these cards in pass, if someone makes a raise.
Of course, you shouldn't pass, if all flop cards are of different suits. If you have nuts straight on the flop in this situation, and someone raises, then most likely, he has set, since it is obvious that on the flop it is not possible to make a flush. In this case, you are a favorite (since he can only win if board is paired) and can play further.
The idea is that in limit Omaha you will play with the nuts-straight, even if flop has two suited cards, because it will cost you one bet per round. But in the pot-limit Omaha, it can cost you a whole stack in one round, if pot is sufficiently large. Thus, the main difference between the two games is the choice of playing combinations, made on the flop.
The role of the position
Position is more important in pot-limit than in limit Omaha. In Limit games, you know that players call bets having draw combinations, and they will call again on fourth street.
But in pot-limit of such things do not happen, because making of possible combination can cost too much. Basically, the main difference between limit and pot-limit Omaha is how many times you'll get to the fifth street in a limit game, compared to how many times you'll do this in pot-limit.
Also, limit Omaha has always more multi-pots, while in the pot-limit games is great probability of heads-up play or play between three players at most (it's very rare in pot-limit with a big pot when more than three players remain in game before fifth street). Either hitting the flop or hitting a draw to the nuts is more important in pot-limit games than in limit.
Top and lowest pair
With a combination of top and lowest pair made on the flop, you can play against one opponent, but if there are more opponents then for Omaha it is not that sort of situation in which you can call a bet. And even more you do not need to play the two lowest pairs. The two lowest pairs in any form of Omaha bring death and destruction.
Suppose you are playing Limit Omaha, with hand with “dangler”, K-Q-J-2, and the flop comes K-8-2. You have a pair of kings and a pair of deuces on the flop, top and lowest pairs. If someone makes a bet, you call and get re-raise, there is a great possibility that you are playing against set, or at least, kings and eights. Then you have troubles.
Even if you have a hand with a made pair, and you have made the youngest set on the flop, you should be ready to throw the cards, if you will be placed get raise. That's why lowest pairs can lead you into a world of misery, if with their help you will make a set on the flop. In Omaha sets are much more common than in other games. A situation "set against set" is a common thing in Omaha, while in Texas Hold'em is relatively rare. If you play in pot-limit on big money, then you absolutely do not need to play game having only the youngest set.