Remember track is measured in diameter - not radius. O-72 = 72" diameter. And, different companies measure from different points - Ross O64 = Gargraves O63. Also, some newer track systems use solid rails and others have built-in roadbed. You're also not limited to fixed diameter track - you can buy flex track, and/or mix diameters to create a custom curve. There's ample choices nowadays whereas in olden times most people just used Lionel tubular (even though Gargraves has been around since WWII (I think).
I prefer track made in the old USA - Ross and Gargraves. There's something both good and nostalgic about that, plus I love the look of wood ties. Cork roadbed is available, as well as various plastic and foam beds.
