I've just started playing around with supersites. As I see it, the page transition feature of the supersite is the draw. I'm thinking the option to have all pages scroll as one might be very useful for mobile devices too. You can convert any regular site to a supersite. If you do not want page transitions on every page, you can set the transition to the site for instant, then set transitions on individual pages. Listed are articles from Xara. On the first there are 3 examples, some where the arrows don't work to move thru the pages, only if you use the navigation bar (which I would want but haven't been able to find how to turn off the arrow key page transition). There is quite a bit of info in the links including how supersites work with SEO. I just started pulling up regular full web templates in xara, then changing the settings to supersite and previewing to work with it.
https://help.xara.com/article/38-supersites , https://help.xara.com/article/465-ho...-on-supersites - does not disable the ability of the arrow keys to navigate. Thought I'd share these articles for others new to supersites.