see if you prefer one look over the other. othrwise, cost. the difference in style is slight.

How big is the space you're tiling? If you have a large kitchen, the 4x12" tile would look better.

it's a small alley style kitchen

We are choosing options for our new townhome. we chose to do white cabinets with black granite counter w black & white backsplash. we are worried about hardwood floor color. We chose golden acacia as shown in attached image. You can also see walnut color which is also OK not as much appealing to us as the golden which will extend into the dining and living room. is it a good flow or not nice at all?

I have black countertops, quartzite island, and medium brown floors. It works well. The island is dark gray.

What is your overall home look? Modern, transitional, traditional/classic? If more modern/transitional the 4x12 will look more appropriate than it would in a traditional setting... You can also make a 3x6 modern by laying it out in a straight grid pattern or even vertically. That being said you can almost never go wrong with 3x6 it's just about the direction you set it.

The house is a 1960's traditional ranch style home. The kitchen is open to the den with a fireplace faced with the original stacked stone in earth tones. It's a fixer-upper house I just purchased a few months ago. Here's the den in the same space
I'd like to add a bit of a transitional to the look, but want to be careful about getting too far from the traditional style of the house

Here's the den, and the kitchen. As you can tell, this is a work in progress! lol
p.s. I usually don't keep my furniture on the kitchen countertops either. (I paint for resell)

the kitchen

Keep it standard size and pretty neutral. You've got a lot going on in the rest of the space, the kitchen should be calming to work in.

I'd say the 3x6. I think it will look good in your space. Good luck! :)