The same place I found the Raspberry Pi 1/Model B? In my cupboard :D I didn't go out and purchase everything brand new for this post. I used what I had available to me! I often see these 2GB models pop up on our local version of eBay and they're out there. Does the newer version have a different SD card reader or other hardware that will render the results pointless in a comparison with it? (Genuine question!)

For the eMMC, quite probably.

The BBB Rev B BOM lists a Micron chip that tops out at 30MB/s read and 6.6MB/s write (pretty close to measured).

The BBB Rev C BOM lists Micron chips in that range but also lists chips like the Kingston EMMC04G-M627 which is capable of 250MB/s read and 25 MB/s write.

This link seems to indicate that the Rev C is around 2x faster on eMMC. https://www.tablix.org/~avian/blog/archives/2017/08/beagleco...

(the RPi Zero numbers seem to correlate with yours so it seems you are measuring the same things)

So, the eMMC numbers are going to be highly specific to the board manufactured.

eMMC sure, but I only added that as a comparison as it was there. This was mainly targeted at the SD card side of things. This post was to show the performance of microSD cards in these specific SBCs, it wasn't a test of the eMMC.