Personally, I would go with an island countertop in a contrasting color.

Definitely go contrasting Color. You have 3 whites…..cabinets and the 2 different white counters, then add a backsplash which I hope is not white. Too many posts on Houzz lamenting the several different whites that people try to mix and then don’t like in their all white kitchens!

I agree with all of the comments already given. My reaction at reading your question and before reading the replies was to wonder why you’d want the different shades of white because I think they'll create a very mismatched look - not what you're intending at all & yes, a design mistake as you worry about . @M Riz caution about the waterfall edge in quartz is spot on - I've read a couple of those threads - very unhappy folks trying to resolve a costly mistake.

Use the same material or an obviously different one (in an obviously different color) for the island. Two whites will look like a mistake.

As others said, this white kitchen is getting blindingly white. You need some contrast and the island is the right place to do it..

So many beautiful quartz materials, so choose a contrasting. Many unhappy posts here about poorly matched waterfalls, as stated here.

You need a kitchen designer to design this project. One who can tell you ”no” and show you why it should be ”no”.

I hate quartz so can't help there but IMO one counter material for all counters when an island is a different color. As for a waterfall not sure how that would help with extra seating since IMO you only have space for seating on the right no matter what so maybe post a pic of the plan for the island counter.

I had envisioned something like this for a one sided waterfall to allow for seating on the other side. It would require 2 jumbo slabs.

Thank you so much everyone for your response. This was very helpful. Much appreciated.

The one-sided waterfall looks unbalanced. Go for a regular countertop with an appropriate overhang (with proper supports) so people can sit at the island. You are “over-decorating” your kitchen at this point.

Not just 2 jumbo slabs, 2 jumbo bookmatched slabs, or unhappiness will follow. There are only a couple of quartz brands that offer bookmatched slabs.

Thi Le:

As you've pictured, an engineered stone top without movement does not need bookmatching. An end with a quirk (the little 1/8" deliberate line between the bottom of the top and the "waterfall" end) does not need to be bookmatched. Without confirming with dimensions, it doesn't appear that installation would require a jumbo slab or two.

What it does require is a custom welded metal frame, I'd suggest 1" steel square tube with the welds ground and painted flat black, to support the adjacent cantilevers. Without support, gravity will sag and subsequently torque the top and that will start a crack at a sink corner.

One color of countertop. Period.

Skip the waterfall, you will avoid endless headaches, I swear you will have headaches with the waterfall you are planning. And, after jumping through all the hoops of the waterfall counter, you won’t like the result. Just get a regular countertop.