I've been using cordless power tools ever since they were invented. I can remember my first one, which was in the shape of a normal drill motor, and used a whopping 3.6 volts. I was living high on the hog, cause that thing would drive a couple dozen 3" screws before running down. We've come a long way, and just as with a lot of other things, it seems like when we reach a certain plateau everyone starts thinking bigger has to be better. If 6 volts is good, then 9.6 is better, and 12 volt is better and 18 or 24 volts is even better yet. I've found, over the years, that my 12 volt stuff seems to have given me better service and lasted longer than anything else that does the same type work. Part of that situation is that I can charge the 12 volt batteries with a car battery charger. When my 14.4 volt or my 18 volt stuff loses a charger, then I'm dead, until I can buy another charger for that voltage, and for the most part they're not cheap, even used, and then you run the risk of using it a few times and looking for another one. So, I'm sticking with my 12 volt Skil stuff. It gives me good service, good power and run times and I can charge it with my car battery if I need to.
40 + years of home repairs and maint. 55 years of using tools and building.