I much prefer the look of just the tile backsplash starting at the counter and going up to the cabinets.
Gaps can be dealt with and so can wavy walls. My contractor in NJ put a "backer board" on the wall to even out the "wavyness" of the wall. It was really not very straight. I don't know if I'm explaining that correctly but there was a large gap between the wall and the counter top for about 2' at one end of the counter top run. The backsplash tile was installed over the backer board from the counter top to the bottom of the cabinets. The finished result was perfect and had the more modern look I was looking for.
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