A lot of knickers getting in a twist about something that has been mentioned once and once only on an 'I have heard' basis.
I was a regular on the DL - ATL and am slightly less so on the VS operated version (although I've already used it more than most would in a lifetime).
Unscientific observations:
1. The Business cabin on the DL76 and the VS 330 are both similar sized and there is rarely a spare seat in either cabin (save for the pilots' rest seat on DL)
2 The back end seems to do ok on both
3. Oddly I have observed that spare seats are most likely found in the Premium Economy section.
4. The bar on the VS gives an opportunity to get to know one's fellow travelers, I have to say it surprises me how many are connecting onto SFO - however 2 per week in the summer ain't going to cut it for the business traveler
Overall I would suspect that DL and VS do pretty well out of MAN-ATL
So I agree it would be madness to cut some ATL for some SFO