I think the chip that's off the block is the one that doesn't fall too far from the tree!
As Steve explained it to me in 2016, the National Semiconductor chips were the originals but when they were delivered they didn't work. So Audionics had to design essentially workarounds outside of the chip. Theoretically, this hampered the speed of the tate system. Mine is a NS composer. I don't have any issues with it.
But Audionics wanted the chips to work correctly, so Exar took an NS chip looked at it under a microscope, found the problems and fixed the biggest ones, but not all, meaning Audionics again had to work around outside the chip to repair issues, just not as many as with NS chips. So in theory, the Exar chips are a little smoother and faster, if those are the right adjectives. I have a hard time telling the difference, frankly, but I am biased because mine is one of the early ones.
Its far more important to performance, in my opinion, to have a stable solid source from your cartridge/preamp and make sure to frequently check input balance with a test record.I do it pretty much every time I start a session where I am going to play matrix records. Steve confirmed that this was key to optimum performance.