The phatnoise cart is sensible; it's a 2.5" drive in a box. The peerless is very strange, they've taken the drive electronics off and replaced it with a buffer board - to make the carts cheaper.

Except they aren't. If you open a peerless base, you'll also see an IBM travelstar mainboard - unscrewed from an actual drive, it looks like. This also limits the capacity, as you can't use drives that are incompatible with the base's electronics.

I have no idea what Iomega were thinking...

Hugo