I agree with the above, that both are great shows and you will enjoy either. I think of it this way...if you have never been to a luau, and you don't mind shared tables (tables of 8 people), then go to OLL. The hula dancers are absolutely fantastic and the whole presentation tells a story. It's truly a memorable experience. If you've been to a traditional luau, or if you know you want your own table for 2, then Feast at Lele is the way to go. The dancing is still good, and if you book early, you're close enough to feel the heat from the fire-knife dancer (I know this from experience). The food at feast is, in my opinion, the big draw. Dinner is some crazy number of courses, broken up by island, to match the dancing. It's a wonderful, adventurous menu that has something for everyone. Take a look at it on-line.
Both are great, on-the-beach settings with beautiful sunsets. Either one will be a memory to last a lifetime and I would recommend either over the other luaus on the island. Have a great trip!