Strange Liberation is probably the most straight ahead jazz of the three, but that isnt saying much. Its a very good disc with a great band.
A Thousand Evenings is a very laid back, with an accordion player on every track. Its a god disc, but its not that jazzy.
Freeak In, wel, the title explains that.
All the discs are adventurous, just in their own way. I dont have Soul on Soul, but Im guessing it is more like Strange Liberation than the others are.
P.S. I would just buy all 3.