I guess you mean EEG, right? I dont know good benchmarks to compare signal quality for these devices.. I think the biggest challenge to create such test is a fact that you cannot record data from 2 boards and single person simultaneously and need to collect a lot of data to handle run to run variability

Visually it seems like Unicorn from Gtec and Cyton from OpenBCI are good. But I have no quantitative metrics for it