Ghost photos at a wedding sounds like a weird sequel nobody asked for. Shooting at 1/15 on a dance floor is basically asking the DJ to help you paint light trails with your subjects. The white blob faces are just your flash saying hi way too close to the action. A faster lens won't fix shutter speed choices, but a decent off camera flash and learning to drag the shutter a bit would help a ton.

Does 9 tons really matter in the grand scheme though?

Same here, attaching real project links made way more difference than any fancy paper ever did.