I have a client that needs a cake to feed about 20 people. She wants it like the one in my avatar. Would it be best to do a single layer 10 inch with an 8 inch on top or just do a 2 layer 10 inch?

Personally, I hate icing stacked single layers of different sizes - unless I board and dowel between. I'd just do the 2 layer cake. Easier to cut and serve, too.

I agree, just do a 2 layer cake.