Benefits and downs of these architecture.

To me both of these architectures are subperb, they both are the best in different enviorments, The x86 is leading in the performance area by a long shot in the pc enviornment, but the ARM is the leader in Embbedded PDAs, notebooks and etc. due to the Low power consumtion of the processor. the x86 in leading in high performance and has not quite got it together on lowering its power consumsion.
Now the good thing is that as far as priceing goes the ARM you may get for a tad bit smaller fee then the x86, which you have to purchase, unlike the ARM achitecture..