I have both the LC 4" VC yellow, orange, white, pads from Autogeek and the SFX 4" yellow, white, from Autopia.
I use both in our detailing business.
The 4' pads don't cause vibration problems with a 5" counterweight.
I have one PC with 6" pad and b/p, and another PC with 4" pad and b/p.
Accum. is right, they're fantastic for removing scratches/defects, better than 6" pads any day.
Most scratches are deep and localized so 4" pads don't waste polish, applies concentrated pressure on a smaller area, and the PC never bogs down.
For defect removal the LC VC 4" pads are better than the SFX 4" pads. The concave shape applies the polish better, and the raised edges applies even more specific cutting on the defect without inducing further marring.
I do the whole car with a swirl removing polish and 6" orange pad, then pick out the scratches with the 4" yellow spot pad.
Then I go over the whole car with a finishing polish and light cutting pad.