I tend to prefer haibun written with a block of prose, followed by a haiku, over haibun written with a haiku followed by a block of prose, but I couldn't quite explain why that particular style works better for me.
I don't know why I'm in such a haibun mood lately. I even wrote one today!
P.S. I think haibun would be very well suited for sf poetry themes, but I haven't seen very many attempt it yet.