It's not all look alike today. Open your eyes. Miele, Sebo, Kenmore, Electrolux, Aerus all have very distinct physical appearances. I think it is especially true of the bagged canisters. Some like Electrolux, Kenmore and Panasonic have some innovation going on in the bag chamber with the bag supported off the bottom of the chamber by a secondary basket (Panasonic calls it Optiflow, can't remember what Kenmore calls it) to maintain airflow as the bag fills. Some allow the bag to be removed from the vacuum in the basket (Panasonic and some new Electrolux models) which is a pretty slick feature. Panasonic's version is like a little picnic basket with a folding carry handle. Some vacs have hoses that swivel from the top while other canisters still have straight end hoses attaching to the front. Suction and airflow of modern vacuums are both vastly superior to the best one could buy forty years ago (look at the weak sealed water lift and airflow numbers of a late 1960s "Sears Best" canister and compare these to what you can buy today). And of course you have the top filling canisters like Patriot, etc. Lots of diversity today.
Btw, one could argue that GE, Kenmore, Royal and Electrolux cylinder vacuums of the 1940s and 1950s were indistinguishable. It is a weak argument for either era.