Squier vs. Fender :
Bassicly everything is different, not the same woods both for body and neck, not the same hardware (bridge, tuners, etc.) not the same pickups and electronic not the same finish, not the same quality of manifacturing, etc.
Bassicly the only thing that is the same is the body shape and neck shape also American fenders are made in the USA and Squiers are made in Korea if I remember correctly.
70's fender and new fenders:
They are a lot alike, construction methods have varied a little over the years, the pickups are not wound the same way and if you are specific about 70's jazz basses, the bridge pickup is closer to the bridge. Also some people say that as the wood ages it ''settles'' and the instument becomes better sounding.