The regular Drake has a 1,000g map rating, while the Drake II has an 800g map rating. The Drake II uses a different bowl wash system, too. The II has the Double Cyclone flushing system. It uses two large vents that release water, instead of a series of holes under the rim like most standard toilets use.
This video shows a different model, but it has the same Double Cyclone flushing system used in the Drake II.
How happy were you with the bowl wash on the regular Drake?
I've had the Drake II for about a month, and I haven't been super satisfied with the bowl wash compared to some other low-flow toilets I've used. But, the other ones I've used were 1.6 gpf units. I don't know how the bowl wash on the Drake II compares to some other 1.28 gpf toilets. It does flush very well, though.