I don't have a lot of experience in this area, but I'll share what small amount I do have.
Uncle Steve was kind enough to essentially gift me a set of Turner irons (I paid for shipping only). I bagged these clubs for about a season and a half and had some really good outings with them. I think they were/are solid clubs.
When I found an old set of TM irons at an estate sale for $45, I switched out the Turners for the TMs for one reason and one reason only: I hit the TMs straighter. (A LOT shorter, but straighter.) I realized after looking specs up on line that one of the reasons I hit the TMs shorter is because the lofts are different; what said "8" on the Turner was really a 7-iron on the TMs, but I digress.
There are other differences between the two sets of clubs, too, that may account for some of the perceived differences; for example, the TM's have steel shafts and the Turners had graphite. So it's hard for me to do a fair comparison.
But the Turners were definitely not "junk" to me, and they didn't impact my scores.