From the 1950's through the 1970's quality was down. Even the pre-64's of that era were not up to pre WW-2 standards and most of those rifles no longer have any real collector value. Winchester was sold to a group of investors in 1980 and guns were technically made by United States Repeating Arms Co., but still used the Winchester name. The 1980-2006 USRAC pushfeed rifles are generally well made and under rated. One of the better buys for the money on a used rifle.
They brought back true controlled round feed rifles (called Classics) in 1994-2006 and made both PF and CRF rifles at the same time. From 1994-2006 only the budget guns were offered with PF, the better finished guns with walnut stocks were all CRF Classics. These Classics were actually better made, more accurate guns than any of the pre-64's. If you can find one, they are the best of the Winchesters in my opinion if you want to buy a rifle to shoot. If you want a rifle as a collectable one of the pre WW-2 rifles, or a post WW-2 rifle only if it is in a rare chambering or configuration is the way to go.
Winchester quality once again started to slip by around 2000. They stopped making guns in 2006. FN resumed production from 2008-present. I'd be a little wary of a 2000-2006 gun. Nothing major wrong with them as a rule, but some often need some weaking by a gunsmith to make things right that should have been done at the factroy. Others are just fine.
The new FN made guns are pretty darn good too. They changed the trigger design which is the only thing I don't like about the new guns. It does have a better out of the box pull, but the older Winchester trigger design was probably the most rugged foolproof design ever made.