Yes Flash is slower on a Mac and Quicktime is Slower on a PC… That is not really the root of the problem.
I tend to be software agnostic, as long as a tool does what I need, I am fairly content…
However, Touch based interfaces open a whole new area of possibilities and problems for developers. The seemingly biggest problem is that current tools like Flash are built around mouse based input. For example, the concept of hover goes out the window with a touch screen.
This example is easy to overlook, because at first it seems trivial. After all, who really “needs” the hover functionality? Well… many sites that I visit use hover for contextual help. Many online games that my kids frequent seem to use hover to track mouse position. Flash does not currently take this into account for things like touch screen interfaces, so if I want to also give quality access the ever growing number of smart phone users, I had better find a better tool for the job.
Now it seems obvious that Apple, Google, and to some extent even Microsoft, think the answer is HTML5 . It does look like HTML5 has the potential to replace Flash in most situations if not all. Here the biggest current problem is that not all browsers support HTML5. Fortunately it seems that the browsers in the latest smart phones and, of course the upcoming iPad appliance support HTML5.
Is HTML5 really the answer? I don’t know for sure, but I would bet that the answer sits somewhere in the middle with Both Flash and HTML5. Flash won’t go away, at least not right away, and the smart ones will not want to leave the upcoming “Coffee Table Network Appliance” users in the dark.

