THe majority of home built machines use Geckos or Rutex because of 1) They work good, and 2) They're cheap. I'm sure those FlexDrives are probably close to 10x the price of a Gecko. I have no idea how AC servos compare to DC. You should ask in the Servo forum.
As for the Camsoft, I can see how it's easier to lean toward Mach2 ($150) versus $2000 to $5000.
