They really are pretty different.
The neck on the Sonus has more the profile of a Jazz bass, so more arrow at the nut and a bit rounder.
While the Legacy has more of a "flattened-out" P-bass profile. A tad wider at the nut and a flatter neck than the Sonus.
In weight, the Sonus is REALLY lightweight, maybe the lightest bass I ever had(I think ash), while the Legacy is pretty hefty carrying around.(2 piece flamed maple body)
In tone, the Sonus really has the J-bass sound going on, but on steroids!
The Legacy on the other hand is more of a growler like a p-bass.
This makes that I prefer the Sonus more for playing in my jazz-ensemble and funk band, while the Legacy lends itself really well to my rockband.
They are both wonderful playing and versatile basses.
I don't ave any sound samples a the moment though..