Yeah...I still don't see it. I really do get that there are people who have had problems with early 556 stocks, and some percentage of guns that shipped have had quality issues (like pretty much any other manufactured product). I don't see that as making the rifle bad, or making any other valid comparisons. How many PE90's have been sold in Canada, in order for us to make a fair comparison in terms of defect rates?
I actually did do a quick google search, and didn't really find anything that supported whether the 556 was as good as the PE90 or not, so I didn't bother to post any links. Some anecdotes about how some bad rifles have been shipped over the past few years doesn't really have anything to do with whether the rifle is as good or not. It does sound like there have been some problems with Sig's inspection process in the past, but realistically that doesn't have anything to do with the rifle design, how long the parts will last, whether it will function under severe testing, etc which is the essence of your last post.
All arms manufacturers have a "scrap" rate for parts in progress as well as finished guns that do not pass inspection, and I'm certain that includes the swiss factory that produces the PE90. The defect rate, however, doesn't reflect on the rifle design or the quality of materials used...it's simply a reality of manufacturing. If we were able to compare actual failure rates for the PE90 vs the 556, I wouldn't be surprised if the 556 experienced a higher rate of shipped defects. Again, it might mean that there's some crappy inspectors that work (worked?) at the plant, but I don't really see how it reflects on the rifle design.
There are plenty of companies that make products for a lower cost than others, yet their products are still competitive in terms of performance and quality. If you could provide a comparison of barrel life, reliability testing, or some information about negative changes to the design then I would be very interested to read it. Otherwise, the discussion is just a matter of opinion.