Why not do the ceiling like the walls or cut 25% don’t make things any more complicated than needed.

First you need clarity on product - what's being used where and what sheen. Then you need samples in each product that will be used on cabinets, walls and trim. These two colors are so similar, that a difference in product is going to matter more than usual. In other words, you can't judge or anticipate results - in this instance - based on color data values derived from paint color chips. Decided on cabinet color first and let that inform trim and wall color. Because you have the most limited choice with cabinet color.

SW High Reflective White will look more neutral, crisp and whiter next to SW Alabaster. SW Extra White has a little less contrast with SW Alabaster, so the combination will appear softer. So it depends for which look you are after. The two whites need to have a perceivable difference in Chroma (colourfulness) in order that one doesn’t make the other appear dirty.

I have had a really busy week and didn't look at Houzz. Hope what I have to say isn't too late for your decision deadline. When deciding on cabinet color you want to choose something that works with the counter you are choosing and works with your overall color palette. Pure White is one of my favorites for cabinets because it is just slightly warm and doesn't limit your other choices as much as either Extra White (more cool / gray) or Alabaster (warmer/ more yellow) If you knew you loved fall colors, warm gold, greens and burnt oranges, I would say Alabaster would work better with the overall palette. That is not what I am hearing from you and not what I am seeing with your other finishes and flooring choice. I think Pure White (left) is much prettier with your flooring than Alabaster. I think Pure White is prettier with Taj Mahal than Alabaster. Pure white will be easier to work with than Alabaster as you make other color decisions for your home. Here is a picture of Taj Mahal with Alabaster and yellow walls. It is a lovely combination. I think pure white would have been too white with the yellow walls and golden floors and may have felt stark, too modern. This is a kitchen with Taj Mahal counters and "Pure White" cabinets. Not specifying SW Pure white, but what I would expect Pure White to appear next to Taj Mahal.