It’s hard to tell which is which if they’re not both in the picture! I think I like the white better. The gray tone seems a bit off with your counter. Although one thing I learned with this counter is it is impossible to photograph. We’re waiting for our cabinets to come in for the other half of our kitchen, then we’ll be able to get the counters done there, then try to decide on a backsplash. I don’t want to decide until all of that is installed. But my favorite so far I think has been a whiteish marble that had almost zero veining. I think I like something that’s basically just on the line between white and gray.

Id do a white subway w sheen. balance out all the gray. there isnt a color that would work . the first pic maybe demonstrates an undertone if you care to search..other just clean white subway...brighten things a bit ... i like the light hitting the upper parts of the white cabinets so i'd accentuate that w more white w the tile. then on to hardware and pendants ???

I'd do a nice light biscuit shade in a subway tile maybe bevelled edge just for the interest.....the gloss would not be a focus for me ....not sure about matte....but just standard ceramic tile I think ... Your light is streaming in from above so how much would hi gloss really impact. You can leave the task lights on a lot if youreally want the gloss I guess....I just dont think that calculation is super valuable . the marble has that warmth and creaminess and subtlety..... but at the same time your kitchen really has scale / that's why I thought a bevel edge to just catch the eyes for some interest , a bit. I'm sure you'll find lots of tiles to work, Nice space!!!! shown: a bit of relief /bevel to the tile edge.....two different shades [funny around a tub-never would have thought to do that] .

It might be best to look at some other subway tile samples, do the countertop as the backsplash, or look at adding some color. Here are some ideas for you from a few designs: