you are right in that there is no point of comparison for b12 and that there lacks magnitude info on the other. i'll have to see if i can find more, but it's not an easy topic to dig up info on.Yes, I know that's what you are claiming. What I am saying is that your post doesn't really help you much with that claim.
Substantive means relevant and substantial. What you provided is just really really thin. My link certainly had more overall relevance than yours because it is broader and it points directly to a particular flaw in your information! The B12 study talks only about one vitamin and only about microwaving. But if "cooking" (methods not specified) can reduce B12 by up to 50%, well then the study that says microwave cooking reduces it by 30-35% in a particular test is completely useless for addressing the claim that microwave cooking reduces nutrition more than other methods, isn't it? As mhselp said, it needs to compare microwaving to other methods to have any value at all.
Your first study is perhaps more useful, but it doesn't say how much difference it noted between the cooking methods and what is done to cholesterol is just one small piece of the puzzle. Obviously, meat is always cooked, but what is probably a bigger issue is nutrients lost in veggies and the differences in losses can be huge, not to mention the difference between cooking and eating them raw! And I don't know anyone who would cook a hamburger in a microwave anyway. If nothing else, cooking on a grill lets fat drain away from it.
My point here is that characterizing this as an issue specific to microwave ovens just isn't realistic and your links just aren't that useful or compelling.