Nighthawk to Orbi - but which one? RBK50 vs RBK23W

Hello everyone! I've been running a Nighthawk router for a while now and love it. I like that it has Disney Circle built in but haven't started using it yet. Probably will soon.

Anyhow, my home is on 3 levels and we also have outside areas and basement areas where wifi is weak. So I'm looking into a mesh type setup and was thinking of trying to keep the Nighthawk but it looks like most mesh systems want to replace it completely, so I came across Google Wifi, EERO, and Orbi.

My question about Orbi is - both the RBK50 (two devices) and RBK23W (3 devices) seem to claim 5000sf of coverage. How do I know which is better for my situation? Is the 23W an older device set than the 50?

Thank you.

Brian