Making a 4unit rdwc is as simply as adding a control bucket, drilling a couple holes and inserting hoses and fittings though. Plus its easy to slowly build it up to a full-blown ucdwc system(mine is in the works

). Never used any type of F & D and they seem really simple to use but it also seems like they have a few up front faults:
system height limits plant height
plant stability
res location inside grow area
water pump timing issues(i just see a flood happening in my room)
largely exposed rw/roots
how do you improve them?
Tons of hydroton for larger setups, though my 8 waterfarms are no better. 6" netpots are gonna fix this, and they can hold trees.
DWC can have problems with air pumps and that's about it. Higher risk for root rot, hard to control temps in single units but rdwc negates this: control bucket outside grow area with ice bottles or iceprobe for smaller setups, chiller for larger. I put my single units into a larger tub with ~20gal and just kept that filled with ice to keep my buckets cool. Take out half and replace it with cold water every 3-4 days.
So IMO DWC is autopilot if you get temps around 65, get a ton of aeration, and use good quality water with a proper feeding schedule, as long as the environment is properly maintained just like any other growing style.
And I'm not just trying to bash E&F without having used it, that was just my own comparison from when I was choosing my own grow style, and my experience/plans/continued research since.