The old Wintel monopoly drove the last 2 decades of computers. In a similar way, software aps will dictate who will win the consumer handheld battles. Apple is having great success here although it sounds like others are catching on.
In the near term, power deltas between the hardware make them somewhat indistinguishable. In the long term, the active power component of the CPU will drive down battery life as users increase their demands on performance*time. This will make x86 less competitive as it cannot compete with risc perf/watt. Intel needs to gain market share before this becomes obvious to consumers or they will never be a major player.
It is rational and predictable of Intel's comeback. Many people may put down to the high consumption for change-hands of Xscale. But if we reverse to several years ago, the smartphone was totally different as of today. The market for mutimedia and smart was not muture enough and the demand was flagging. Even there was no mobilephone company that can put the strong capability of computing into application. Xscale was ultimately abandoned by Intel as a "premature child".
Nowaday smartphone is actually a computer that happens to make a phone call.