Well, having also trained with S&W TDA pistols for many years, and being a certified LE armorer for S&W, Glock and Sig Sauer pistols, I can say that the DAK does not have a single action trigger function. It has a couple of enhanced DAO trigger positions.
The primary trigger stroke (longer stroke) requires approx 6.6 lbs of pressure to fire the pistol, although it 'feels' lighter ... and the intermediate (shorter reset position, so to speak) trigger stroke requires a partial reset of the trigger and approx 8.3 lbs of pressure to fire the pistol. When I asked why the shorter, intermediate trigger reset required more pressure to fire (just curious), I was told that Sig Sauer felt it was safer for the shorter trigger reset position to have the heavier weight.
As far as reliability? Well, Sig Sauer pistols are often considered to be over engineered in some senses. They increased the strength of their slides for the .40 S&W cartridge, and the frame insert (think locking block) makes for a strong design.
One thing to remember about Sig Sauer pistols, however, is that they require good lubrication in order to run. As was explained in the armorer's course, and repeatedly emphasized during the course (including being a test question), Sig Sauer pistols must be 'wet' to the eye, and 'wet' to the touch as far as the required lubrication points. Otherwise, function might not be as desired and excessive wear may occur. Of course, they also caution against over-lubrication, as well.
I think Sig has the advantage when it comes to having metal-bodied magazines.
I think Glock's trigger function and feel is more to my liking, but that's totally subjective, and you didn't want to focus on trigger function, right?
I think the Glock recoil spring assemblies should be changed more often in the .40 S&W models (and 357SIG) than many folks apparently think, and even Glock armorers are starting to be told this.
I think the Sig Sauer recoil springs should be checked, as well, for sharp edges on the inside, and especially for the core element to recede and/or the spring elements to start spreading. The .40 S&W cartridge generates a lot of recoil forces which act upon the guns (and the 357SIG generates even more).
I think that with periodic maintenance inspections and proper care both pistols are fine for the common defensive uses ordinarily expected of handguns in this caliber, but I also suspect that it wouldn't be surprising to perhaps see the Sig endure a bit longer.
Then again, I've only fired more than 40,000 rounds through a single pistol, and it was an issued pistol, at that (and a S&W). I really don't plan on ever running that many rounds through any of my personally owned pistols, since I don't compete ... and not to mention the cost factor
... so it's not an issue for me.
If you were to shoot both platforms on a course or two, in different weather conditions, which required strong/weak hand shooting (both 1 & 2-handed), strong & off-side barricade, movement during shooting, multiple target engagement and such, you might be able to better answer your own question regarding the shooter-pistol interface and the practical performance of both designs ...