I'm no clown expert but I've seen what I consider super reduced here and there so they're not totally a rare occurrence. On that note I do see more regular/semi reduced on the market though by far.
I like brighter clowns with lots of orangey/yellow tones over the darker/tan brown ones. On here: http://www.worldofballpythons.com/morphs/clown/ I love the snakes in pic 2,3,4,9,and 19.