The Mini Amp Gizmo is specifically designed for amps that have complex footswitches and proprietary footswitch connectors. These amps require a Mini Amp Gizmo and an interface cable made for that specific model of amp. Amps like the Mesa Rectifier and Road King series, Bogner Ecstasy and Blackstar HT Stage series are examples of amps that work well with the Mini Amp Gizmo.
The Switch Gizmo is made specifically for amps that use 1/4-inch mono or TRS jacks for its footswitch. No special interface cable is needed, only the appropriate off-the-shelf 1/4-inch cable(s). It works with a variety of amps including the Marshall DSL, Mesa Lonestar, Mark V:25 and Mini Rectifier and many, many others.
The Amp Gizmo does everything that the Mini Amp Gizmo does and also has four TRS jacks for direct connection to amps that have 1/4-inch footswitch jacks. The Amp Gizmo is the preferred choice for people that need to control more than one amp (one or more with 1/4-inch footswitch jacks, and also one with a proprietary footswitch connector).