The energy cost difference with regenerative braking is essentially negligible between these two cars. Adding several hundred pounds to my EV driving around makes little difference by my measurements. And as to the idea of the lithium being wasted, that might not necessarily be true as well. Its not like those extra cells will never be used, its just the pack will never really hit 100% charge and will never really hit 0% charge, it'll essentially always be somewhere above 0% and below 100%. This will allow better wear leveling over the whole pack, so if the car is used a decent bit it'll get more miles on its life than the smaller pack.