There's no doubt in my mind that the DA could produce a high gloss finish that parallels that produced by the rotary.
When working with products such as Ultrafina and PO85RD, with the rotary I could break down the product very quickly and with very little pressure. This is due largely to the rotary action.
With the DA, I using a product like PO85RD, it takes longer to for the product to break down (from haze to clear). I also have to put more pressure onto the machine to keep the pad stable and to adequately work the product in. The added pressure required to operate the DA MAY be that little factor that reduces gloss. It may be, but not certanily. The added pressure demanded to operate the DA may also deplete the polishing oil sooner than the abrasives have completely broken down.
My observation is from that when I work the SIP into the paint using the DA and a white polishing pad. While the product goes completely clear on the paint, the pad is still somewhat "gritty" to the touch. This doesn't seem to be the case, or not as severely, when I work with SIP using the rotary. Perhaps spraying some water onto the pad to continue buffing may resolve this problem.