For me, I hone my razors up to an 8000 grit stone and strop to polish. I shave in a North/South first pass and a South/North second pass. On my face this is a combination of WTG/XTG and ATG. The XTG occurs on parts my neck.The first pass leaves a bit of felt but not seen, stubble. The shave doesn't feel uncomfortable in the least. The second pass gives a 98% BBS shave and is still comfortable.
I have experienced a much cleaner first pass after our friend Jimbo came around to check my honing technique, and touched up my razors on his (much finer) finishing stones. The shave was even more comfortable at that level too, however, the end results were the same. The first pass still didn't give a perfect BBS (which is to be expected), and the second pass still left those small areas, where for the life of me I can't get the angle just right, with a little bit of roughness to them.
The idea is to reduce the beard on each pass. With a straight razor you have a single blade doing one pass with lather, then a second after re-lathering and so on. With a mach 3 you have three blades covering the same ground. The first takes some hair and the lather away, then number two and three blades come along running on bare skin to take away a bit more each, which is why a modern blade is more prone to give you irritation and ingrown hairs, and also makes for a smoother WTG.
In the end a straight razor will give the better shave, as the other factors involved, beard prep and technique etc all play a part and leave your face the healthier for it. Yes, you could use all the same prep and shave with a mach 3 or similar, but you are still giving yourself a two blade dry shave in every pass, and that can't be good for the health of your facial skin at all.


Mick