Nothing you can say will convince me to buy it. Not because I think it's crap or anything, but because I'm not a beginner DM. The only things I use the DMG for these years are magic items, traps, XP tables and optional rules chapters. I have all 4 of those in the 5e DMG and the 5.5e DMG removed one of those. The only temptation I have to buy it is the Bastion chapter, but I can't justify spending that much money for a single smallish chapter.
You didn't say sidebars, but outside of the optional rule chapter, most of the optional rules in the 5e books were in sidebars. It doesn't really matter if they are sidebars or sprinkled in. That's a distinction without a difference. I want to know if the number of optional rules sprinkled about is comparable to the 5e DMG optional rule chapter, and I've been told by those who have the DMG that they aren't.
The reason I'm asking is to see if I'm right and it's just a few, or if there are a significant number of optional rules.