Hello Ivan!
I think the first thing to consider is what type of cuisine do you think you would be interested in? The Tusker House is a buffet that has a wide variety of choices including some African inspired dishes along with some of the standard buffet items like cold cuts and salads. Yak and Yeti is an Asian inspired restaurant with items like lo mein, duck and stir fried vegetables for example.
Since you are on the deluxe dining plan, Yak and Yeti would definitely be a better use of your credit. Since this is a meal where you would order off of a menu, you would get to choose an appetizer, entree and dessert and get full use of the options provided with your dining plan. On the other hand, since Tusker House is a buffet, you would have the opportunity to sample everything available.
I would consider what kind of meal you are looking for. If you want a more relaxing experience, Yak and Yeti might be for you since you can remain at your table instead of getting up to visit the buffet. I suggest visiting
www.allears.net to look over the menus for each restaraunt. From the allears home page, click on "Dining" at the top of the page and "The Menus" on the left hand side.
I hope this was helpful! Have fun planning your vacation!