Personally I like the step side, but that is just a visual prefference. I think asking which of these is the better material, based on just looking at the pictures, is like asking which is the best CA finish.:wink:
From my limited experience, I find that some of the vitage materials have a softer, warmer feel in the hand. I have also heard that some of the vintage formulas are smooth as butter when it comes to machining. Visually, I have seen modern acrylics with a similar appearance to your french acrylic. Are they worth the price? Only if you can sell the final pen for proportionally equal high price.
I have recently moved into the calligraphy world, which is becoming quite popular. There has been a number of discussions about the value of vintage nibs. There are some nibs on ebay and other sales systems, that a few years ago, would have been going for a couple of dollars a piece. Keep in mind, when these nibs were origionally sold it was by the grosse. This was because they wore out very quickly, they were a consumable tool. Today these same nibs are getting sold in the $30 range, simply because of market interest. I have heard a number of professional calligraphers say that while these nibs are good, and in some ways superior to modern nibs, they are not worth that price.
I haven't worked with any of the vintage materials, so far only moder ebonite and cumberland. Either I come to late to the party when they are offered or, more usual, I don't have the funding when they are available. While I know there are clients that will pay more simply because it is a vintage material, its hard to justify the cost on speculation. Hopefully one of these days, I will find a deal that will let me get some of these to try out.
All that aside, they are both beautiful pens.