Both the Allen & Heath SQ-6 and the Soundcraft Vi1 show up regularly on the second-hand market, and both are capable consoles. The right choice depends less on the spec sheet than on how your operators actually work.
Allen & Heath SQ-6
The SQ-6 is a compact digital console aimed at live sound, installed rooms and rental stock. Its draw is a fast, touchscreen-led workflow and a footprint that fits small control positions.
Soundcraft Vi1
The Soundcraft Vi1 sits in the Vi family and carries the same console philosophy: a familiar channel-strip layout on a large surface. For operators already trained on the Vi range, it is a short learning curve.
How to decide
If your team rotates and needs to be productive quickly, favour the console whose workflow your operators already know. If you are buying for rental stock, favour the one your clients ask for by name.
Buying either one used
On a used console, faders, encoders and touchscreens are the wear items that matter. Ask for a photo set showing each of these tested, not just a front-on shot of the surface.