Intriguing Bill, that's the first time I've ever heard that the G50/5x has a beefed up case. Do you have any specific details?
How hard can the G50/0x be run? Probably quite hard, but for how long? It comes down to how sticky your rear rubber is, and how much torque that rubber allows you to put through the trans. Not to mention your driving style and whether you treat the thing with some mechanical sympathy or are just some ham fisted un coordinated twit!
A G50/0x may be good for setting a record breaking 0-100-0 time, but if you drive it like that all the time how would it's longevity fare? Since you are asking the question 'how hard can it be run?' maybe you really are a candidate for the beefier trans. Only you know the treatment you are going to give it. Only you can decide which trans you need to run.
It comes down to peace of mind, if you are going to give it an unmerciful thrashing, do you want to be living in fear that your not inexpensive /0x is about to lunch itself? Not to mention the inconvenience when it does...How expensive is it likely to be when/if it does destroy itself? Would it not be better to put a little more cash up front and be less likely to have these issues in the longer term?
But for 'normal' (what is that???!!) everyday driving I'm sure a /0x would be an excellent choice. Probably also a reasonable choice if you run it hard, but how hard and how often? Who knows.....If you are continually hard on it, that oft repeated phrase may apply here......'You can either pay now, or you WILL pay later!'