There have always been production differences with vacuum models, and the long-run Hoover machines are no exception. Even the Electrolux Model G had at least 4 variations if you include the Hospital G.
But I am questioning if that's the case with the new Hoover canister. I visited last month with an old friend who runs a shop in Louisville and he follows vacuum manufacture very closely. According to him, TTI has a very competitive bid process for manufacture of their machines. Vendor A may get a contract to build 500 machines for $X, then Vendor B gets a contract to build 1000 machines for $Y, and so on. This is for the same model. Chances are that the differences you see in these two Hoover canisters represent manufacture by two different subcontractors.
I suppose TTI owns the basic moulds for the vacuums, but the other parts, such as switches, motors, filters, etc are bought from the cheapest vendor. Everything is outsourced these days, even in the East. Still, differences make a model collectible.
John