Kilgore Trout has a much greater depth than Robert Henlein.
Depends upon what you want. KT (aka K. Vonnegut) is great at social satire. His characters are wild and unusual. RH is great at plotting and simply telling a story. His characters are well drawn, but he only has about 3-4 types of characters that he re-uses from book to book. RH has some political axes he likes to grind, but I often agree with him, so I don't mind. I much prefer RH to KT (or KV). I have read all of RH's novels and many of his short stories. I've read Venus on the half Shell, Slaughterhouse 5, and one or two others by KV.
No- as noted by someone else on this thread, "VENUS ON THE HALF SHELL" was written by Philip Jose Farmer (an author who seems to me to be virtually unreadable).
I have a copy of "VOTHS", though, and if it's worth "thousands" as this story indicates I may have to auction it off on eBay!!!