prefer? Chocolate cake or a butter cake? Any other good combos that I'm missing?

Chocolate or white or butter would work well. Or a combination of them.

I did chocolate and white for my nephew's birthday with cookies and cream filling. I torted them then layered them chocolate, white, chocolate, white. Yummy!

I use a scratch devil's food cake with my cookies n cream filling.

My logic the first time was that the cookie in an oreo is a rather dark chocolate, so the filling aught to taste good with that kind of cake! Everybody since then has tended to agree.

It might also be a matter of taste. The devil's food cake, with the filling and a chocolate icing is definitely uber-rich. A french vanilla cake would be less intense and still blend with the filling flavors.

I love oreo cookie filling with rich butter yellow cake. It is YUMMMO!

I recently used it with the double chocolate layer cake from Epicurious.com with rave reviews.

Oh wow, i bet that double chocolate cake was intense, that's such a rich cake to begin with!
Thanks for your replies, I think I'm going to do a butter cake.

I like the idea of alternating chocolate and butter, but I really don't need that much cake around the house, lol.