PJ2
I have only once been to the aerodynamic ceiling and that was on a VC10. I was young co-pilot at the time and the training captain took it up to 46,000ft. Where he demonstrated the low speed buffet and the high speed buffet and I was permitted to do so too. There was about 5kts between the two. As I remember, the high speed buffet was of a sharper quality and at a slightly higher frequency - but memory does play tricks. I also suspect that each aircraft would exhibit slightly different qualities. For example, the heavy low frequency vertical motion of the 747 clean is quite different to the VC10 and 707.
Perhaps some of our test pilot colleagues could enlighten us on the stall characteristcs of different types under different conditions.