The circuit similarity between tuners is something many probably won't realise but there is a small selection only of IC's used as IF subsystems/quadrature detector and stereo decoder. A similarly small range of pilot tone suppression filters are used at the output and a few companies only produce most of the "front end" boxes....
So? you may be asking? So unless you are buying something really exotic the innards of most tuners are almost identical no matter what make or model!
Sure one can find things that break the mold on this but they are few and far between....
E.g throughout most of he 70's and 80's I'd guestimate that 90% of European and USA tuners used CA3089 (or the later improved CA3189) IF amp and quadrature IC followed by the MC1310P stereo decoder IC. There were (and are) Japanese equivalents which are pin for pin compatible. A later generation of such IC's then came into use but probably a range of say 3 of the former and same of the latter type of IC was/is used in most tuners. Quadrature coils made by Toko are almost universally used, single tuned type in cheaper models and double tuned in better ones. Toko or Murata made pilot tone filters are almost universally used as well. Little wonder then that so many tuners have a similar sound. The precise way these parts are used accounts for probably most of the differences we do hear...