70 degree vent temps... dude... you been scammed LOL!! Thats someone who is just too lazy or doesn't know what he's doing and is passing off BS to get his pay and move on..
Sure.. the original refrigerant is the best thing to use, but... since you have to have a license and its hard to procure, using r134a is a reasonable tradeoff. And no.. it doesn't work as well IF you JUST drop it in and do nothing more. You sort of have to "adjust" your old A/C like we discussed. I hit the sweet spot in my red car.. new modern multipass condenser (the OEM tube&fin one will not do the job), new (or adjusted) pressure switch, orange Otube, and charged just right. I get 34 out the vent on recirc.
Now here's the conumdrum.. IF... and its a big IF... your system is leakfree and in good condition, you would never have lost cooling in the first place.. So its (therefore) broken by definition. You must repair it. For most of the time though, you never have the chance to repair before the compressor goes. When the compressor goes it suffers what is called black death. You essentially have to replace everything under the hood to fix it. This means a new condenser which is only made in the modern 8mm multipass type, compressor, liquid line, and accumulator. Since you have to do all of that anyway even if you stay with R12, making the jump to r134 is not that much more work.
As for HCs.. I might be willing to consider it, but I honestly don't have time to mess with experimenting with it.. so I stick with what has a track record. BTW.. of your list... only Duracool, Envirosafe are actual HC refrigerants.. 2 are r134 blends. Freeze 12 for instance.. the number 12 means well..... it means 12! .. has nothing to do with R12 its purely a labeling gimic.