I'm not going to argue that SouthWest, JetBlue, and Virgin America provide a better coach experience than the US legacies. In my years (and hundreds) of flights on DL Mainline I can't think of a time in which I've had unacceptable experiences due to the cabin staff. I'd agree, WN/B6/VRD are consistently better, but DL hasn't been bad. Is it as nice? Sometimes. Is that enough to offset all my upgrades? Negative.
That said, I'll agree my biggest gripes and variance in service levels have been on the regional carriers. I've complained to DL many times that the coach experience on the RJs, especially the single-class CR2s (the tiny ones) have ranged from great to unacceptable. That has to be doing damage to DL's brand and, to their credit, they are limiting regional carriers or upgauging to aircraft with F, and the cabin crew apparently get upgraded as well.
Now, to the level that regionals are "less safe" - perhaps at some minute statistical level - yes. But for practical consideration regionals are just as safe as mainline.
Patrick Smith, a Delta 757/767 FO states:
http://www.askthepilot.com/questiona...gional-safety/
On the other hand, I remember myself as a young, 500-hour pilot and imagine being assigned to a regional jet. Would I be qualified to the letter of the law? Sure. But am I the best and safest candidate for the job? No. The reality is, there are valuable intangibles that a pilot that green simply does not possess. Therefore, I suppose it is fair to say that regional airlines have become, on some level, less safe. Mind you that we’re wrangling with statistical minutiae: less safe is not the same as unsafe, and this is by no means an admonition against flying aboard RJs. Nevertheless it warrants our attention.