Flooring Tile - Slate / Granite joint

Hi, we are remodeling our house and have a dilemma. We want to lay 16x16 slate in our kitchen/den area. However, we want granite tiles in our foyer/entry way. How do you handle the joint where the two materials meet at the beginning of the hallway?

Also, an interior decorator recommended that we not use the two materials, but rather use one material throughout. Any opinions? We want the kitchen/den area to be more informal and thus have chosen a 16x16 Indian Copper slate. However, we would like the foyer area to be more formal so would like to go with granite. Thanks.

Two of the same category of flooring but different styles doesn't look well next to each other, unless your are creating an intricate design.

Although my thinking would be for it to be the other way around, you could go hardwwod in the entry, but stone entries are better then a hardwood.