I use the bought shaker, with methylated spirits. Just because I'm locked into that as my approved method for testing bees for export to Canada. The Co2 method came along after that, if I was starting again that's the way I would go.
However apart from export bees where testing is mandatory I don't test the hives, it's too time consuming to test them all, I just assess by the look of the brood and the bees, and the general vibe the hive gives off.