A good size is one that you find comfortable to use. Hands differ in size: order a couple pulls to see what feels roomy enough.

What Color or colors of Counter Material would be more complimentary? The islands are currently specified to be a satin/matte gloss black finish or not shiny with some rub through for distressing.

I think a good thing to remember is cleaning. If they have detains that dusty grease can get trapped in they will be harder to keep clean. Simple is better in my opinion. Just another consideration. And then the price... good luck. I really like the choices you have made, black island, white outer cabs, and stunning natural stone. Beautiful

Agree with apple-pie: Get samples of any hardware you’re considering. The projection of a pull or knob will matter a great deal to whoever has the largest hands in the house. Your cabinet style is traditional, so there are lots of options. Have a piece of wood you can attach the samples to so you can literally feel how hard or easy it is to use. (We put smaller than usual pulls in the master bathroom and it’s difficult for my small hands to open them.). 5 inch pulls would be the smallest you should consider. Large drawers, if you want one center pull, might need 7 or 8” pulls at a minimum.

The larger the better, and do NOT get open ended ones. They catch on clothing.

Agree with Deb.