The worst one was the pre Raspberry Pi 3 boards. The early ones used an on board Ethernet chip set that was slaved directly to the USB controller. It was USB 2.0 so it could negotiate 100, but really run much less than that.

Then, if you put in a keyboard, mouse, and a USB thumb drive the USB host would multiplex over them and your bandwidth for data transfer would drop precipitously.

I was so happy when they moved to a real Ethernet chip instead of a USB adapter. The new limitation became the microSD... Of course they also introduced the grounding reset issue on the USB port, but just don't plus or unplug anything and it'd be fine.