Interesting opinions
 a really lightly loaded model  needs none and for really complex aerobatics - differential can get in your way

  It is easy for  one's own flying techniques  and basic cg setups to  mask roll errors 
 for example :
some guys hold in a smidgen of  up or down elevator  all the  time  in upright flight
 seen it over  -n over  etc.. when doing a roll  - the  elevator trim causes the roll to look goofy  . 
they fiddle with differential trying to  get  the  wallow out of the  roll.
  The  ATV setup on some radios will  affect the  throw (up vs down )and cause  aileron response  which again appears to need  differential.
 The reason for  differential in the  first place - was  to compensate for  the  yaw -which occurred on just about any  full size sport plane  and  the  rudder  /aileron blending was used to  fix this  skidding
 Now here is  a neat trick if you have not tried it
 On a design with as much fuselage side area  (effective side area) as  wing area - you don't use  ailerons to bank n turn - only to roll . so  NO differential wanted or needed
 to turn these  you just  add rudder  - that's it 
 the  fuselage  provides  the  lift normally lost in a turn
 I know this will cause  some  to  faint dead away  in disbelief but  -it does work.