They both run Honey Comb but the A500 is 3.1 where as the A100 is 3.2.
Ram is 1 GB on the A100 dual core Tegra chip. (512 on each core).
As far as rooting, soon I hope.
The gift card deal is over but possibly you may convince a manager .
Down side is keep your charger handy 4-5 hours run time.
Spec page link.