Interesting, I have one MKS Sbase so I might test this, not sure if the Sbase is the required 1.3 version though. I do like Reprap FW, I have couple of Duet boards and they work very well once you get them set up. Same goes mostly with the Marlin based boards, excluding RAMPS, I really don't see very striking difference in everyday printing, all machines do their job once you get them set up. Some of the machines I use are still 8-bit and I really haven't seen that much difference in overall printing, sure some of the small segments print faster on 32-bit and 32-bit boots up bit faster, but nothing earth shattering.
On Reprap FW the configuration is easier once you get to know how it's done, everything is gcode and configurable in the web UI, no need to recompile the fw to change things. Also Reprap fw is very flexible in the configuration, so in this is a big plus when working with multiple extruders and more exotic setups. On Marlin I had to modify the Marlin code to get a custom relay setup working, on Reprap it was few lines of gcode in config.

When coming from Marlin, the initial configuration is involved though, so depending on the printer might take some tinkering. The online configurator helps a lot and gives you a good basic config to work on. I got my first RAMPS -> Duet conversion done in few hours, but it needed some tweaking of course. Also setting up the bed sensor needed some soldering due to some voltages being different on Duet and RAMPS.
After the setup it gets a lot easier since all settings can be controlled in UI