First off, it would be impossible to accurately determine the difference in hit from cue to cue if only the joint was different. Every cue will hit (slightly) different even if it has the same pin and it's made from the same species of wood because lets face it, wood grows naturally and no two pieces are exactly alike. That being said, there are ways of controlling the production process (such as coring the forearm) to minimize the difference in the way each cue plays/hits from a given maker. Still, unless the cue was made out of a man made material such as plastic, metal, graphite, ect. each one will play different.
As far as the G10 breaking I have heard stories of Joe Gold actually taking a cue durings a shop tour for a customer and throwing it into a bench like a dart to prove the durability. So leads me to believe that the chances of it breaking during "normal" use is pretty unlikely.
I think the OP is a little off base on why the makers are using the G10. Yes, there is a good chance they would use it to get to a target weight of a cue but it will also affect the balance point.
Paul Drexler and I had a long conversation one day regarding how the style of pin will change the overall weight and balance point and that he will sometimes use a different pin to get the desired result the customer is looking for.