For starters the s8 line is the replacement for the s5 line basically. Supposedly better all around. The s6 line is straight suction only ( doesn't appeal to me). I would say get the s8 uniq if you can afford it, I like having all my controls on the handle or at least to turn the main unit and PN on and off. It just b
Econes a matter of options they all use the same motor.