I must admit - not knowing anything about the history - I always assumed the Hohners and Spirits were the same thing with a different logo.
The Hohners came out first didn't they?
yes, i believe the hohners came out in the mid-80s. the spirits came out in the 90s. they are made in the same factory, with slightly different appointments and finishes. the most obvious difference is the tremolo - the spirits have roller saddles, the hohners have normal ones. the switching is also more versatile on the hohners. the differences and german branding give the hohner variant the edge IMHO.
i put the tonal differences in mine down to different wood - also i changed the bridge for a fancy one on my old spirit which surely makes a difference. the fingerboard on the hohner has quite a bit more oil in than my spirit, looks better.
edit: my thoughts about the sustain are wrong i think - its impossible to choose between the two actually. its late and i'm hearing things. quality wise the two are pretty close as well
cool-ly the hohners were originally also available with twin humbuckers, with or without a trem. the come up sometimes on ebay. in the 80s they also had some quite nice colour schemes, including a diagonal schenker looking one.