Then go for it! There's no right or wrong, but it might cost you a bit more to do diagonal because of all the extra cuts. Be sure that your range can still be levelled to the right height if they put new floor under it and not under any of the cabinets!

My choice would be the top one - horizontal

Either horizontal or diagonal, the middle option makes the room look narrow.

The only issue i have with diagonal tile layout is the transition to adjacent flooring. It can look very odd, depending on the cuts. Assuming your kitchen opens into a dining or living rooms, measure and sketch the your layout starting at the edges and see how it works with the cabinets' toe kick.

I prefer the horizontal myself. I think the diagonal is too busy. What's going on the countertops?

Our counters are granite - Salinas is the name.

Do you have a picture of the tile? That'll help figure out which layout would work best.

The granite doesn't look too busy, what I'm seeing on google anyway. Can you wait until the slabs are installed to see how the veins flow on the counters?

I would do the vertical (second photo) as it leads you into the room.

Picture of our slab here. Counters being installed this weekend. I would imagine that the veins will run parallel with the length of the room.

Beth - do you mind sharing a pic of your tile? I'm interested in what 18" looks like

I would stay horizontal, it will make the room feel bigger, the vertical, IMO, will make the room feel narrow. I do not think you gain anything by going diagonal other than more costs. I like the stone that you picked, it will go well with your cabinets.

I have a long narrow kitchen 3.5m with only 1m floor space between the cabinets on each side.. I have put rainbow slate tile (12"x12") in the diagonal way. After trying all the patterns, the diagonal layout made the kitchen look MUCH wider. After 15 years I still am very happy with the result.