This thread is relevant, too: https://forum.inaturalist.org/t/monitoring-gardens-and-spreading-the-message/26094
Yes, equipment definitely makes a huge difference. This doesn’t have to be anything as complex as microscopy, dissection, or DNA sequencing – my experience is that even just having a macro lens radically changes what one is able to document and identify.
I was reading an article about urban balconies as habitat for pollinators (in a different city but the same country as me) and one thing that struck me when comparing the author’s list of her finds with those on my own balcony was the differences in what we had recorded. She had more larger animals (a greater variety of birds, a squirrel, a lizard), but I’ve documented over twice as many species overall in a shorter period. Does the mere number of species tell us anything about the relative biodiversity of each of our balconies? I doubt it. A considerable portion of what I’ve observed are well under 1 cm, and many of them are smaller than half a cm. And it mostly these tiny organisms (springtails, barkflies, etc.) which are missing from her list.
I think it’s really hard to make any sort of meaningful comparison or draw conclusions about the diversity of a specific property for such projects, because most of them do not involve any systematic monitoring, and there is so much variation in the choices people make about what to record and their resources for identifying organisms. (Not to mention different property sizes and environmental conditions – suburban vs. urban, tropical vs. temperate location, etc.).