From looking at Apple.com, their PPC life is generally 1-2 hours less than P-M systems. As for P-M vs. Turion, as of right now, P-M systems are faster for video editing due to the large L2 cache. I think PPC hardware design focus more on efficiency for video editing in conjunction with their OS, but this design is not perfect for every software, likewise with Intel/AMD.
Considering the 64bit windows/unix with Intel's dual-core 32 bit, 64 bit P-M (2006 with 4meg L2) plus RAID! and higher overall speeds across the board, PPCs may lose its edge(or reputation) for AV editing performance. Futur AMD Turion based systems are also worth the competition. More things to consider is that some PC notbooks right now have muti HDD capability which is better for swaping and scratch. I'm not sure which current PCs can do firewire800 thou.
Editing on batter is also tricky. I can't find any benchmarks that contrast PPC with Intel/AMD at power saving mode. For instance, how will PPCs power saving technique compare with intel/amd interms of performance vs. battery life.