The Differance
The main difference as I see it is how the system engages the tire. The stanton friction type uses a frame that had been around for decades where by you use some sort of locking mechanisum to "affix" the drive system with preasure onto the tire. This makes it a rigid system and more difficult to balance preformance with changing road conditions. It is also why I think you hear about bearing complaints with the other friction drive systems.
The DE friction drive "floats" on the tire with a self adjusting tensioning device that keeps the proper amount of preasure on the tire w/o overdoing it. I think it is much like a "self tensioning" belt system for keeping belt riders from shedding belts.
Roller wise he has three options, wood ones that you can get from him or he will explain how to make your own, Eurathane for a cool look [what I use], and an "all weather" one that will raise the tire wear a lot but works in rain, snow, and mud. The other guys use that knurled metal one that I have seen get hot enough to melt cheap buytle tires.
Tire wear. If you use knobby tires they get smooth fast, lol. If you buy "blue light specials" that are not real rubber they wear out fast. I have always used "police or Trick Bike" tires that are high preassure rated and with a road tread. They need to be made from real genuine rubber just like an auto tire. Anymore as I don't ride as much one tire lasts a year or two, at worst I went thru 2 tires a year but I buy my tires from Rob at DE, call him and ask him how many miles he thinks you should get based on how you want to drive it.
He does his own web design, I hear from a lot of guys here it seems they don't like his page. Call him and tell him what you like about others page's.
So in a nutshell besides an engine and that its friction drive it is completly different from the other's on the market. All of the mounting stuff he makes himself and he uses higher quality and where torqe is applied larger diameter parts. For folks that use centrifical clutchs, [ I don't.], he even makes them in house. Frankly with his system you don't need a clutch but he offers a better one for folks that "insist" on being like everyone elses.
Like you I want zero drag when pedaling and when I want my engine I want it now without stopping or doing gymnastics on a moving bicycle.