Thanks, Frank for clearing up a bunch of confusion, for giving Duncan credit for a knot he came up with in the 50's or early 60's (now called the uni-knot), as well as for your last sentence which is absolutely accurate.
I've recently come to the conclusion that machine knot-testing just don't mean a whole lot, and different people using the same machine will get different results with the same knots every time. It's all how uniformly you can tighten them like you said- and that's mainly a matter of feel, practice and lubricant.
Also, knot strength often isn't the issue, as with shock (often now called "bite") tippets. Some knots will cause trolled lures to spin; loop knots are more prone to causing enormous salt-water flies with long hair to foul around the hook/hooks when casting or landing, and so on. Some, like the "Rapala" (in my opinion) add unnecessary "anti-slippage' measures, which weaken the knot by making it nearly impossible to tighten properly and make it bulkier at the same time.
Some take too long to re-tie, some use too much tippet to re-tie, sometimes neither of those things matter at all.
There just isn't one knot for all situations.
I was curious like Nedun about why your leader butt to fly line connection breaks before your fly to tippet connection too, Ard - unless you are "unsporting" like me.
I run straight 60 lb leader on my 12 wt for big fish - which exceeds the strength of my actual fly line. But both exceed the strength of the hooks I use, or the hookup in the fish's mouth, and I'm able to handle them much quicker. I also use 80 something pound test backing.