For sure - if you can afford them, get both. I was just surprised because I expected to use the SA a lot more when I got it. But I am mostly either testing filters are designing antennas, and the NA is the way to go.
I guess what I'm asking: What features of the NanoVNA make it the "way to go"?
FOR ME: It's the PC SW that allows a big-screen, which converts the fundamental "R+jX" measurement into many different views. https://nanovna.com/?page_id=90 Awesome.
I found, for what I do, having a vector network analyzer was more useful that having a spectrum analyzer. Specifically, measuring the SWR of antennas and measuring the resonance frequency of filters.