I wouldn't have thought they'd wash raw rice before selling - sounds like a recipe for encouraging mould and bacteria. There will be different varieties, with varying taste and textures, but whether you can tell the difference I don't know. Perhaps cheap brands are hulled more crudely, resulting in broken grains, stodgy rice etc... just a guess.
When it comes to basmati, though, that certainly does have a different, appetising taste and smell to regular long grain. Worth the extra, IMO.