I had been wondering about this for some time, having bought a GameCube this year with GCLoader being a thing now (wish we had a Swiss-style front end for GDEmu). GC power supply is a dinky little thing and I would think to be better quality than the Pico-style PSUs that have been made for the Dreamcast (Nintendo surely put some money into R&D on them anyway).
I don’t have the ability or knowledge to test if the put the same current into the various voltage outputs that the Dreamcast PSU does, I’d like to see those numbers.
Additionally, the Nintendo external DC brick puts out 37.5w which is sufficient for the DC. I’d imagine these to be pretty good quality, likely better than anything you’d find on Amazon etc. You can use these with a pico-style PSU in the Dreamcast if you change the connection on the end to suit.
I’d still like to see someone test the genuine mini-box brand pico psu which can be used with those Pico Dreamcast converter boards. They should be fairly solid in terms of performance vs the China clones or the other Dreamcast options.