The video isn't choppy, it's just a small screen. It's got decent resolution and speed. I've watched youtube videos and some movies I loaded up from my computer and they look perfectly fine, just not my first choice for multimedia. I had an iPhone 3G before this, and I still use it for any multimedia purposes. As far as that, the Aria can't compare.
The processor I believe is 600Mhz. It may be 667Mhz. In the Android system info app 600Mhz is the highest listed speed so I'm about 90% sure that's the processor speed. I do know that it has an ARMv6 (I think that's right) processor. Whatever type it is, whehter v5 or v6, I read on XDA forums that the 3.0 Android OS will most likely not run on that type of processor. That's not a definite, but most likely because it's outdated technology or not fast enough, something like that.
If you have any other questions don't hesitate to ask.