Well, I have owned 2 Galaxies, and 1 Super Galaxy, but they were old Galaxies. They all had Reynolds 531ST frames, but different equipment.
My understanding is the "Plain" Galaxy is made of Reynolds 631, and the "Super" is 853, and has slightly tighter angles.
Now, if you're doing what these bikes are supposed to be designed for, loaded touring with racks and panniers, any arguments about bike weight are a bit silly. So it's best to try them both and see which one you like.
Personally, unless they are a good deal, I don't really see the point of the Galaxy anymore. They used to be expensive, but a lot cheaper than a custom frame. Now, they aren't. Of course, that doesn't mean they're a bad bike; it's just that you can get something more special without spending any more money than the list price. So have a look around.
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