Well, I'm not squall, but I'll give you my opinion for free this time, the rotation of an ETS combined with the softness of the pad can cause roundovers when you go over an edge, and that's not desireable. You do not have this problem with the linear motion of a DTS or an RTS. The pads of the last two are harder too.
If you have a hard pad on a rotating sander it is not that much of a problem either. But unfortunately in all their wisdom, Festool decided not to make a hard pad available for the ETS 125.