The differences and similarities between 50's blonde (and subsequent Butterscotch bar-tan) and the later 70's naturals is difficult to explain.
They're probably better understand in terms of the 'perceived' or 'desired' result, rather than the 'actual' result. Or, in other words, what was Fenders objective with these two finishes?
It can be seen that 'blonde' finishes produced by Fender starting in the early 50's all the way to this day are designed to �color' the guitar in a way that allows for a limited amount of grain to show. The objective here is not to showcase grain, but to use grain as a decorative element. ~ key word: TRANSLUCENT PAINT
These are the finishes that later oxidized to the well-known and well-loved Butterscotch color, or as ReRanch calls it - Butterscotch Blonde (a.k.a. Peanutbutter and other pet names like honey- blonde etc.)
When Fender caught wind of the popular trend among guitar owners in the late 60's to strip the paint off Strats and Teles, they predictably began doing 'Natural' finishes on their Telecasters and other instruments. .~ key word: TINTED LACQUER
The objective here was to sell guitars to a generation of guitarists who were victims of the 'back to nature' movement of the late 60's - early 70's. A factory Fender Natural finish is of course NOT simply a clear coat over raw wood. What it really amounts to is a tinted coat that allows all the grain to show fully.
A better example of a natural finish on a guitar might be the lightly satin finished 'white' necks of the current crop of Squier Strats and Teles. In my view, the anemic look of those necks (as opposed to the beautiful rich amber of vintage Fender necks illustrates clearly just exactly why Fender elected to darken the ash of 70's 'Naturals' by adding TINT. Aesthetically speaking darker natural is more attractive than lighter natural.
Of course, there are exceptions and various gradations as one would expect. Also, peoples tastes change. Some may prefer lighter natural over darker natural. As it was, Fender went with darker. Most of the 70's natural finishes I've seen are amber-like and quite attractive. Most benefit from bar-tan to a degree.
Actually, my personal �72 Natural Tele has a decidedly Butterscotch flavor to it; distinction being, of course, that ALL the grain is exposed, unlike the 50's guitar blondes.
What makes a 'factory' blonde or natural superior to a refin must be seen strictly in terms of the refinishers abilities and the quality of the products being used on the guitar being refined.
I am convinced that with the correct products, an expert can reproduced virtually any finish regardless of vintage. Non-expert refinishers unfortunately are in the majority, which probably explains why most refins are less attractive than 'factory' finishes.
Remember also that the Fender factory had at its disposal large buffing machines; vats of 'wash-coat'; tubs of Fullerplast; and shelves of color sticks, paints, dyes and pigments with which the employees could work minor miracles.
A company such as Fender does not achieve such success without knowing how to do it right. And they did.
Louie Seven