Renig,
the problem with bossa nova styles is that the bass player usually plays behind the beat (at least he does so if he is really brazilian... ), whilst in those Yamaha styles the bass is always dead right on the beat and this kills that relaxed feeling a real bossa nova should have.
Besides, I hate the T2 bass sounds and I wish that Yamaha had included the beautiful acoustic bass of the Motif ES instead...
Another thing: I usually mute the string track in all bossa nova styles because it tends to give a corny feeling. Sometimes I leave it, but with a vocal sound instead (like a Hmmm choir).
In general, I like more the bossa nova styles in the PA1 X pro: they seem more "on the money".