There has been a running debate about stamp hinges, and how Dennison has always been the best, etc. I thought I would add my two cents worth.
I've been collecting since the middle 60s, and I bought a good sized supply of Dennison hinges at that time...50 years later and I am now running out. I have been buying hinges for the first time in many years, including some vintage Dennisons. Some of the newer collectors and maybe some of the old timers may be interested in my findings.
I took a sheet of computer paper and stuck 5 hinges that I had on hand across a line of print. I had both modern Prinze and modern Supersafe hinges in house as well as some hinges that I have had for a long long time. Some old hinges that were sold without a brand name were identified in small print on the back of the package as being made for "The Treat Hobby Company". Treat doesn't seem to be around any more...I can't find any modern reference to them. They have a green tint, and appear to be made by the Dennison company. I also had an envelope of unfolded Dennison hinges, and one more recent purchase...some hinges sold as "Hygrade" which also have a green tint and may have been made by Dennison.

I then peeled off the hinges. Dennison and Treat worked as well as expected, leaving almost no residue and causing no damage to the paper. Prinze and Supersafe both left a bit of residue and both thinned the paper just a bit. That may or may not be visible in the picture. The Hygrade worked well, not thinning the paper at all but leaving just a bit more residue than the Treat and Dennison.

I don't know, but have been told that there is only one company making stamp hinges today...the company that makes Prinze hinges. If that is true (and it sounds very likely) Prinze and Supersafe are identical hinges (as well as any other currently made hinge). Granted this is not exactly a scientific test...but the two hinges tested as much the same as you would expect of two batches of the same brand name...and they look to be the same.
The long and the short of it is that I am happy with my current stock of hinges. I will use my supply of Supersafe and Prinze on cheaper stamps and use Dennison/Treat/Hygrade on most of the stamps I hinge for as long as I can milk them along. If I were to buy any hinges in the future, it would be Dennison or Treat, and Hygrade as a backup. If you are interested, there are some Hygrade hinges on the market right now for much less than Dennisons are going for. I don't know that all batches of the brands I have are the same...I just tried what I had.