Due to the manga being of the same author they share the same esque, humor and absurdity. Although Palepoli is more comical, the garden has its own bits of funny moments. The biblical references are present in both manga and I can't get enough of them. Give it a read I say.
Plastic Girl and Palepoli are made by Usamaru Furuya, and would both not be concidered "manga" at all if Furuya-san later decided to actually do manga. Plastic girl is a short arty piece about growing up, and if it weren't for a few details this could almost be read as a feminist manifesto (due to the few small details it can not though). Just as surrealistic and unconventional is Palepoli, but it is based on humour and actually tries to mimic the 4-koma format (and fails). The bonus part in the end, created when Usamaru Furuya still was in college is the most funniest and most disturbing thing I have ever read, so be sure to check that out.  read more
Both manga contain different dreamy/trippy short stories, Palepoli is more comedic, while Shounen Shoujo Hyouruuki portraits common problems in a bizarre yet creative way.
Both are made by the same author except Shounen Shoujo Hyouryuuki was written in collaboration with Otsu Ichi, another great similar author.