I have been using PEx cinch clamps about a dozen years and have never had a leak either from installation or afterwards that I know of. Never had a call back on cinch fitting and I give a written guarantee with every job. So I do have complete confidence in the stainless steel system. But I have not heard of anyone having problems with the crimp fittings either. I am talking about stories from actual plumbers or fix-it types. There are stories on the internet about PEx failing, but I tend to believe that is mostly dyed in the wool, copper sweat fitting plumbers stirring mud. I can see where PEx plumbing, using any kind of fittings, is an imaginary threat to plumbers.
So my personal opinion is that both crimp and cinch are excellent plumbing methods. I think the pros and cons are more about application than performance. I like my stainless cinch fittings because #1, they are stainless steel. I was a mobilehome tech for about the last 10 years of the polybutylene plumbing era. The crimp rings kind of creep me.
Also, I only need one crimp tool to do any size fitting, 3/8" to 1". The 1/2 & 3/4 is all I actually use. The bad thing about the cinch fitting and tool is that you must fit the tool square to the fitting. I have closed the tool and went a little sideways on the fitting, causing me to cut the ring off and try again. To my knowledge, there is no small cinch tool for tight places. While this has created challenges, it has never stopped me or even slowed me down much with the plumbing. Just like cpvc, steel and copper, when I am in an area I can't reach in to, I make the hard to reach parts one assembly and put it in as a unit. Another thing I like about the cinch tool is once you get it calibrated right, the tool does this "collapse and click" to let you know when the tool has done it's job right.
With the crimp system, you need different tools for different sizes, unless someone has come up with a multi size tool that I am not aware of. There is the small hand tool to use in tight places, but that crimp is not as accurate as it is with the big crimp tools. It is also important to use the go-no go checking tool with the crimp system. The stainless cinch system does not use them.
The cinch ring is a lot more engineered also. There is a stop built into it so you will know when you are fully seated. You can see the engineering in how the ring actually does "cinch" or tighten evenly around the fitting and you don't end up with the two bumps like on the copper ring.
As for which is best, I am probably no help. I prefer the cinch. Most folks on this forum use crimp. I doubt anyone here will give you stories of PEx failures using either system. It might come down to user preference. I know for myself, when I saw those same rings that we used on PB pipe, I did not have a lot of confidence in the crimps. Back in the PB day, rings often failed right at that crease on the bump. But that was an aluminum ring problem on the old PB pipe. Never had the problem using copper rings on PB pipe.
Today is PERFECT!
All information and advice given is for entertainment and informational purposes only. The person doing the work is solely responsible to insure that their work complies with their local building code and OSHA safety regulations.