Battery life is similar in that the life of said batteries is about 500 charges or abotu 18 months and the capacity starts to dwindle. About year 2 and you replace the battery.

I haven't seen much variance caused by choice of base CPU.

Runtime however seems to be more affected by simple items like how bright the screen is or if your application runs the CPU at full tilt.

Without specific make or models, the runtime minutes are likely to be very close to each other and I bet I could cause either model to trade its lead position just by dimming the screen a little.