Interesting one, this.
A dishless SS cassette or screw-on hub will, in theory be stronger, and therefore can be built lighter.
I’ve just sold my DMR Revolver on 717, and I’m going with an old Hope XC on 317. The reasons for this are simply that, at some point, I may want to run gears on my Singular Hummingbird, and also that two rear wheels for the bike was a bit of a luxury. Otherwise, the only downside I could see was that, if I wanted to change ratios, I was a bit stuck. I’d have to buy another freewheel at vast expense. It’s not really been an issue before, mind.
The DMR has been completely reliable, and the WI freewheel I ran for the last three or four years has had not a single hiccup. I stripped it down recently, and aside from a quick degrease and re-oil, it needed for nothing.
In short: screw-on hub for a cheap build, but you’ll have to pay through the nose for a good enough freehub. Or just buy a standard wheel and spacers and run your choice of sprocket. You can then use it on other bikes as and when you want.
I looked at the singlespeed cassette hubs a while back, and they seem like too much of a compromise, if that makes sense. You have to pay an (albeit) small premium for them when you’re pretty much, to all intents and purposes, buying a normal hub.
My advice: if you don’t trash wheels regularly, just get a bog standard rear cassette wheel and space out a sprocket. It’ll be cheaper than a SS cassette hub, you can use it on geared bikes, and you can change the ratio as and when you like.
HTH!