Performance-wise, with the same cartridge and in the same system, I think you would be hard pressed to tell much difference. That said, the 512 does have better specs. And the VM95e is a step up from the AT71E (which is very, very similar to the older AT95e).
PL-115 has a sprung-suspension, PL-512 is a solid plinth with "shock absorber" feet to reduce external vibrations. The rubber bushings in these feet is very prone to decay/rot, after which the "shock absorber" function is lost. Replacements are available, although they are of a different design and are not cheap. Alternatively, I have had very good success with a solution that looks good and will cost less than $10. Won't take up space in your thread unless it turns out that you need new feet.
Note that questions of price are supposed to be posted only in the Dollars and Sense forum. You can use the "report" link (bottom left of each post) to ask a moderator to move it for you. Or you could edit out the pricing info.