ARM
Pro:
I think the PCB is easier to design, makes it cheaper to build and faster to get it working.
Reuse parts, software base and knowledge of the pandora (makes it cheaper and easier to produce).
Feels like the GPU with ARM is faster, could be wrong there. We need it for gaming, so the CPU/GPU combination must suit those needs.
I can't think of any cons! (that is just me, there could be plenty I can't come up with now)
Con:
X86
Pro:
PC OSes, software and games.
Build for the masses (even non games might be buying it creating bigger sales).
Con:
Leaving current pandora base behind.
Not sure what the new Intel chip requires, but the X86 use to come with bios and all such additional chips you do not really want on you tiny board.
People not interested in the community will get it without respect for ED and the project, might lead to additional stress/work/costs.
One thing that might be good to think about is: "What would the successor of the Pyra look like?".
If it might use the X86 the switch would mean a better software base in the future.
And in the end I doubt if the CPU architecture would really matter to me as I probably still want the device.
(looks like no-script kills your lay-out in the posts
)