Texad De Brazil and 'Ohana are very different. 'Ohana is very family focused and have games to keep the children occupied. They have only 4 meat selections and the meat is not of the highest quality, sometimes tough to chew. At Texas De Brazil, there are 14 types of meat and the most amazing salad bar. They also serve wonderful Lobster Bisque. 'Ohana serves lettuce as their salad, nothing else in it, but I love the dressing they have. They also have these great little dumplings.
You said that you are wondering if the extra cost is worth it for Texas De Brazil, but if you sign up on the Web, they tend to send quite a few coupons. We have generally only paid $25-30 a person when we eat there so 'Ohana ends up about the same price.
I would say that my decision would come down to the age of the children in the party, whether you will have a rental car and want to go off of property, and the amount of time you want to spend on dinner. It takes us about 30-45 minutes longer at Texas De Brazil. Also, one thing to know is that sodas are not refillable at Texas De Brazil for free, so it gets pricey if you drink soda and want more than one.
My answer is that if you are going strictly for the food aspect, Texas De Brazil would be the way to go. If you are looking to have something the kids would really enjoy from an overall experience and strictly a Disney experience, 'Ohana is the way to go.