If the G6 also comes with a spraybar, you could increase the size of the holes with a drill. Lots of ways to control flow. I just think the G6 is a better buy, even if you don't need that flow. The larger cartridges will increase the time prior to needing to be serviced. as well as maximizing replacement costs.
I'd consider the G3 a viable option if it was a few hundred dollars less...but it's only about 10% cheaper then the G6. The pricing scale of those things is so messed up right now. I don't really see the point of the G3 currently.