Hey RLB…
The answer in part, depends on what you’re trying to accomplish. Introducing waterstones into your lineup, can result in a more refined edge, in part because waterstones break down, so they’ll sharpen/polish at a higher level then what they’re rating is. The tradeoff is you have to account for stone wear (which is where the new arms really come in handy). You can also get a “crisper” edge off of waterstones, (easier anyway) since they don’t tend to round the edge like a strop might.
The other part depends on the knife you’re sharpening and what you’re cutting.
Of course, if you enjoy sharpening, it’s fun to get a variety of stones to play around with and see the different results you can get! 🙂