Bob,
If you held everything else the same, the surface area of the shaft of a std TTS tool holder is about 3.83 sq inches, while a 1" shaft would give about 5.5 sq inches, around a 30% increase. So at first glance, it would seem the 1" holder would resist pull out better. Whether it would be enough of an increase in holding power to make it worth starting a new line of tool holders, I can't really guess. I'm sure some of our smart guys could give a better reply.
Terry