I use Dragon Shield, KMC and Ultra-Pro.
But have there been any quality control tests that show statistically one brand is more reliable than the others?
I have not seen any independent quality assurance tests comparing the various sleeves, and I sincerely doubt there is a comprehensive one to be found. It's probably not economical for anyone involved, since QA comparisons like that can be quite expensive.
From anecdotal evidence at my local shop, which has ~80 player FNMs every week, most players seem to agree agree that:
These are the three most popular sleeve types at the shop.
I haven't seen any QC tests but I have been using both over the past year. I have every color of Dragon Shields (except Brown and Pink) and I have only had an issue with 1 set (some tearing on about 10 sleeves). I double sleeve my cards using Perfect Fits on the inside and I riffle shuffle. that puts a ton of stress on the sleeves
Ultra Pros are good, not as thick as Dragon Shields, but I haven't had an issue with them. However, I've seen many of an opponent tear an Ultra Pro midgame.
I always put it to my friends this way... In the lifetime of a box of sleeves you can buy one box of Dragon Shields or 3 boxes of something else.
I'll share my experience on sleeving matter.
While the sleeve quality is important, but your sleeve durability also greatly affected by your shuffling technique. So, if you shuffle correctly (i guess), then at least ultra-pro (I specifically recommend the non-glare one) is decent enough. not to mention it's somewhat cheaper than KMC.
I personally loves ultra pro, since I am able to double sleeve it without being too thick. There's a non-glare variant too, which is I use to double sleeve my modern deck. So far, my subjective rating for Ultra-Pro is 9/10, and KMC is 8/10 (mainly for being too thick to double sleeve.
Hope that helps.