They are not all the same.
A ache vette in 1976 had a PCV valve that only flowed .7 CFM. Normal Chevy V8's flowed 2.8. The V8 valve placed in a ache vette would not really affect how it ran, but would empty the crankcase in no time. Once they realized they had a problem chevy had the Chevette units plastic T cast with pink plastic to make it stand out. The aftermarket did not.
There are thousands of different PCV valves, many look alike. But they flow differently, open at different throttle amounts, and close differently. Spring rates are different, valve shapes are different, internal passage sizes are different.
For this reason it's better to use a factory (Delco, Ford, Mopars) valve that is close to what yo are running, or even better, a Moroso crankcase pressure control valve. With this valve taking the place of the breather or breather tube and adjusted properly to maintain a crankcase pressure of 5-8" of vacuum, you keep the rings pulled in slightly at cruise, reducing drag, you make valve seals, rear main seals, and front crank seals that may not be all that healthy work a lot better. You now don't really need a PCV because The Moroso part is controlling air flow. These pieces work great. The next step up from that is an all out vacuum pump, but if you aren't racing you don't need that. If you race once in a while you may want to T an aspirator from the header collector in, but make sure to place a check valve, like from an AIR pump into it so the Moroso valve will still work.
Simple things make big differences.