I don't think that the use of Mylar bags and oxygen absorbers has been around long enough for a real comparison to the long-term storage results of a can. I have quite a bit of both cans, purchased from the normal providers, and Mylar packed, done at home.
For barrier properties, a properly sealed can just can't be beat by other common packing methods. That said, a properly packed mylar bag is so close to a perfect seal, particularly with an appropriately sized oxygen absorber, that the difference is effectively insignificant.
Quailty Mylar bags pass so little oxygen or moisture that properly packed foods would last as long as in a can. Even after the long-term storage taste and quality tests published by BYU, the end of usable life wasn't driven by nutrition or spoilage but rather by taste and palatability. That is going to be the same in Mylar or a can.
Even though I vacuum my Mylar bags, I still use an oxygen absorber to handle any oxygen that enters through the bag itself. Of course, for some fragile foods such as egg noodles, I don't vacuum but, rather, I rely solely on an appropriate oxygen absorber for preservation. You'd be surprised how much the bag compresses under that circumstance. Since quality bucket-sized Mylar bags pass less than 1cc of oxygen in 3 years, that oxygen doesn't even have to be considered when estimating the oxygen absorber requirements.
I expect my Mylar packed food to last as long as my cans of the same food type.