The Fuji is a nice old bike, but not a tour machine, by what I can see in the pics - which isn't much. Looks a little close-coupled with short chainstays. Also, that's a road double crankset, not a mountain triple, which would be better for touring. Probably alot of fun, and just the type I'd like to add to the stable for grins.
The Miyata is probably as good as they got back then. Deore is rock solid stuff and the bike has all the hardpoints for attaching accoutremon. I'm an advocate of Shimano BioPace/Sakae OvalTech chainrings so that would be a huge plus for me. Totally knocks down the hills, especially if it has the 28 granny.
Now, I paid $550 for a mint '98 Trek 520 last year, fully dressed out. I think that Miyata is every bit as good a bike, probably as good as the old Trek 720. Maybe someone can add to this by confirming my hunch that it has Ishiwata tubing???
$675? I think the seller knows what he has. I'd be sorely tempted if it's in great shape.