I finally switched to the new Blogger. And I don't see any major differences to my template at all. This or the other one. All that worrying for nothing.
It is indicative of my attitude towards change. The way I've been drug kicking and screaming into the 21st century speaks volumes about me so I'm not surprised I took so long to accept the "change" to new Blogger.
I do have to integrate the new labels and archiving features. But as of now, it all looks fine.