All of your responses are good to read .... for Lou, I lumped the two together, because (at least here in the U.S.) the publishing world lumps them together. From what I understand, the pioneers in the area (i.e., HG Wells and Jules Verne, etc.) told their stories in and out of both genres, and so the two seem to be very strongly linked and many (though as you prove, not all) love both genres, even though they are distinctly different. But also, many of the writers go back and forth between both genres and so bookstores tend to lump them together so that the authors works are all together (hopefully selling more of their stories to those who enjoy that particular author's work).

At least that's some of the reasons I've come across as I've been pondering some story ideas in these two fields.