It's hard to say, they're all different and great in their own ways. Wretch is their sleaziest, it's just a pure rock album kind of like ACDC's Back in Black or something like that. Blues For the Red Sun is mainly their desert sound, it's a bit more experimental, as is Welcome to the Sky Valley. While ...And the Circus Leaves Town is probably their most artistic and psychedelic, fairly different to anything before it, some of the songs are much more mellow.
http://www.albumbase.com/list_albums...uss&cat=artist
Theres no Wretch there but i'm sure you could hunt it down somewhere.