Battery life depends on many things and I can't think of a laptop than has two modifications with only the cpu being different. I know that an eMachines M6809 with AMD 64 3200+ mobile has battery life of ~3hrs for light usage. The ferrari 3200 has battery life comparable to this, or at best 20-30min more, however, while the cpu is a low power AMD 2800, the Ferrari 3200 has a more power-consuming gpu. If, and this is a big IF, all other components have about the same power consumption, I would guess the Low Power AMD 64 2800 in the Ferrari will give ~1hr more battery life - like snorre mentioned.
Of course, you have to make sure that you can put, i.e. it is supported, a low power AMD 64 in place of a Mobile. I would be very surprised if they aren't compatible but still you have to make sure that is the case.