It's not simply a matter of better or worse..
The newer models that John made, with the bowl pads are about coloring the signal in a fun and pleasing way (if you like the color, which I do not)
The older models that Joe made were about the fidelity or purity of the signal- neutrality and transparency.
So one is not better for everyone, it depends on what you want out of audio gear. Old vs new grados represent polar opposite philosophies and approaches to what headphones should accomplish. And while I prefer the approach of the older Grados, the fact is that the newer approach (whether it was the sound change, or some other change in marketing or elsewhere that John made) saved the company from going out of business.
I think it's likely that it was marketing changes that saved the company moreso than the sound changes, because I don't think people really knew about the Joe Grado phones. As someone else said, he was ahead of his time and likely didn't know how to market or advertise his products to communicate to people what they were about. But whatever it was, people bought a lot more of John's phones than Joe's. But marketing aside, if the HP1000 was still in production, a lot of people would prefer the RS1. People used to be a lot more vocal on this forum about thinking that the HP1000 sounded boring, but now they have a legendary status like the K1000, which seems to make some like them who wouldn't otherwise. So it's really just a matter of preference and what you want.