Purity aside, there is no correct answer to this question because it all depends on what compound we're referring to.
When it comes to testosterone, there is a shit-ton of UGL-made test that is every bit just as potent as any pharmacy-grade test from the 80's. This is because test is cheap to synthesize, so there is less incentive for people to be unethical.
Now, when it comes to stuff like Anavar, Primobolan, and Halotestin (very expensive to make...about 3X as much as Anavar according to a recent manufacturer's price list), your chances of getting properly dosed UGL-made gear goes way down. It's still out there--it's just that a much smaller percentage of what's available is real and properly dosed.
...and then there are a bunch of other AAS with prices throughout the middle range.
For this reason reliability will vary greatly from drug to drug. So, if someone says "80's test was way stronger (inferring proper dosing) than today's stuff", that may be true some of the time, but there is also plenty of UGL-made test that is equally as strong. On the other hand, if someone says "80's Halo was way stronger than today's UGL stuff", that statement will ring true the majority of the time.