the “pixelated blocks” replace the old overlapping gray circles. from what i could tell, the gray circles covered things up more, given the same zoom level.
i assume that when you’re talking about “dot density” maps, you’re talking about this new map with the red squares arranged in a grid, and i assume that when you’re talking about heatmaps, you’re talking about the kind of map being discussed here: https://forum.inaturalist.org/t/show-heatmaps-of-our-observations-and-identifications-on-user-profiles/1613. i think in the way they are usually created, a heatmap starts its life as a single-color opacity-scaled density map, similar to this “dot density” map, except that its “dots” are oversized (so that they overlap) and blur into each other. then a color gradient is applied on top of the result of that. so i think that means that a heatmap with the same underlying resolution is going to take more processing power to generate.