I've grown photos on and off for a long time, new to autos. Trail is right many strains are just fluffy. But most of my stuff is very dense, and it seems a mix of decent lights and adding a good bloom booster has helped. Higher P&K has seemed to make a decent difference. Autos and photos no difference, but my landrace kush has had the densest buds while the sativas have been looser.
Note on the lights, my LED's/cobs/QB have produced denser buds than the 400/600 HPS I was using. I have a mix of 3000 & 3700 in one tent, all 3000 LED & 3500K Cobs in another and 3000 LED & 3500K + 660 QB in the last (brand new, yet to harvest). I would have to grow all of the same strain in all the tents and not move the lights to really know, too many factors. Just listing as a heads up.
Note on the neighbors stuff, more than likely if it is either from a LP or black market CO2 was used and that will help.
Honestly, it's too bad so many people equate rock hard buds with quality. I have gotten so much shite from dispensaries that was rock hard and utter crap. Also it can be a mold magnet. But most people who have bought seem to be sold on the "hard nugzzz = top shelf" it's hard to convince otherwise.