I'm not speaking from a personal view of either bands contribution to music history, I love both bands. But think of it like this: I can probably count on my fingers the number of times I've heard Pink Floyd on the radio (even on retro stations), or heard a coverband play one of their songs. Sweet Home Alabama is still one of those songs you can't get away from, both on the radio (be it retro station, classic hits, golden hits or whatever they all may be called). It's also something you still hear many coverbands play. Personally, I've never played any Pink Floyd songs in any coverband, but I'm pretty feed up with Sweet Home Alabama
In the last full time band I played with, we added pretty much anything to the repertoar, as long as it was it was requested enough times. Sweet Home Alabama was played at pretty much every gig, no Pink Floyd songs. So my point is still time same: There is probably more general mass appeal to the wider public in Sweet Home Alabama than any Pink Floyd song. Again, not taking anything from either bands, their members or the quality of their work, just recognizability and "fame". But hey, things might be very different, but in the northern mainland of Europe, this seems to be the case.