all I know is my saab 2.0L engine is top notch, very torquey from just off fast idle, and can get me just under 40 mpg if I drive it light... And is easy to drive reasonably and get good acceleration, etc (that to me means that i dont need to go over 3500 RPM to get GOOD acceleration and power) I dont see many powertrains like this coming out of other manufacturers, even Honda. To me it says something about 'GM' powertrains.
Ive been really happy with my 98 ZR2 as well, though Ill admit there was a slight (without UOA Id have nevr known about it, as coolant level never changed) intake manifold gasket leak.
Our corolla and previa have had rock solid powertrains. No issues, no complaints. Neither were sludge monsters either. But, toyota radiators suck, the previa and corolla both had radiator failures too early, and, my GF's 4 runner, which resides in the USVI had a similar thing.
In actuality, my GF' acura has had more issues over, say the first 150k than our two MBs and our toyota. though this isnt reflected in any of these studies. nothing significant, just minor things (including radiator), that all cause her to stop in her tracks/breakdown due to some silly thing going bad and needing replacement. Then the car is great again. But $ value and number of repairs - the honda is far worse than at least toyota and MB. Thre MB may not be fair, but the toyota comparisson is.
All in all, I think that there is litte difference between GM and toyota powertrains, and if they were both maintained equally, Id venture to strongly suggest that they would last about equally. And each would need certain things, likely different things, replaced on each, toyota or GM. In the old days, Toyota was far ahead. They still have more, more economical vehicle/drivetrain combos, which says something about toyotas ability to put out energy dense, high efficiency powertrains, which means that their engineering be better... (on a side note, see more hondas burning oil with a visible plume than any other make... the second worst? dodge caravans... but that to me indicates something about the longevity/duraility/quality of honda engines, vs. toyotas, which would likely have the same level of care, use, etc., and I don't note (and smell) the same thing).
I doubt there is any real significance between 16.7 and 18.1 problems per 100 cars. Id bet also that that 16.7 or 18.1 probles were also spread between only 2 or 3 vehicles; they just were lemon cars and had multple issues, which each counted.
JMH