Hi Bowsaw!
The Interstate model features different/wider site panels (square shaped) and a longer seat to match the bigger fuel tank. I found the riding position quite awkward, i.e. uncomfortable. Mind you, I am just 5'10'' in height… a Fastback Norton is more comfortable in my view.
The overall looks are far more ”tour” than ”sports”, perfect for sustained long distance riding at 70/80 mph.
So you ask which Commando to go for? Well, in my pov, you can choose any Model, no matter what year of manufacture… as long as it is COMPLETELY overhauled: the engine carefully reassembled (refined parts, belt primary drive is icing on the cake!), gearbox taken care of, boyer ignition, carbs make- over, new fork internals, new rear shocks, disc/drum brakes fidling, vernier adjustment on the isolastics and some other bits and bobs. You are talking BIG bucks here… think of ca. $ 10.000,00 at least. But then your Norton is built to last,creates envy and admiration wherever you go… and the pride of owning one is priceless.
Verdict is, the better bike is the better buy.
Best regards from Hamburg, Germany
Matt