I thought your post was in reference to using microSD cards with an SD adapter, not micro SD vs SD generally. Hence my specific reply pointing out that there's no difference between them unless you have a duff adapter.
Regarding SD vs microSD, as the OP has pointed out, the price difference can be significant, and as I've pointed out, there's probably no difference between SD and microSD for the same class of card.
Point being, there's no inherent reason why a microSD should be slower than SD for the equivalent card and therefore if there is a significant price difference, people might as well go for the microSD with adapter over the SD card. Obviously if you require the speed of SD cards that don't yet have an equivalent in microSD form, then of course SD is the way to go... although I see Lexar now offer microSD up to 150MB/s vs SD at 300MB/s, both UHS-II.