per-level makes sense since you hit lvl 8 pretty quickly and the per-level runes are stronger after that point.
I currently run:
health quints (for an edge out of the gate... irrelevant later though)
straight armor yellows (for strength in that first encounter... as a tank i dont always go bot)
mr/lvl blues (because the heavy magic dmg doesn't come until people start buying offense items)
and mpen reds, because most of my preferred tanks do magic dmg.
I'm almost always getting glacial shroud -> frozen heart anyway to the lower armor mid-late game from using straight armor yellows is made-up-for by the items I get. Often I find that MR items aren't as useful as the armor items though so I need those MR/lvl runes for late-game. I don't really like Odyn's because I always forget to use the active, and abyssal scepter just feels so expensive... often the only MR i'm getting from items is from Lich Bane and the tenacity boots.