[OtterBooks]

The upcoming Nook has the most advanced CPU, contained in the Kobo as well iirc. How it translates into actual performance, I don't know, as there are likely other factors at play. That's about the closest any of the devices come to being 'most advanced'. All other characteristics are either equal, or differences in design that can't really be measured along a performance scale (different interfaces/form factor).

Jury is out on battery life, but I hear the new Nook can go 25 years on one charge. Battery life calculated based on reading one minute per day. Kindle is only 12 years.