Personally I only root/rotted at the very lowest levels. My Druid was an alt, so my main got him a Goblin Gazughi Ring early on and then he was off to SK to charm elephants and such, followed by Rathe Mountain bears, then LOIO windmill tigers, and then I went to
Cazic Thule to charm alligators for like ten levels (click the Druid filter on the
Per-Level guide and you can mostly see the path I took, along with some extra ideas).
I did nothing but charming until 45 when I picked up a Lumi staff and started doing the giant fort in EW. I also did some quadding in EJ (it started with quadding the apes to try and make the guy for my epic spawn, but I discovered they weren't bad XP) and in WL with 4s/6s. But ultimately I did all the hard levels up to 60 charming in the Permafrost Bear Pit.
I don't think any one technique is better ... scratch that: root/rot is pretty clearly worse than either of the two alternatives, XP-wise. IMHO once you're able to charm/quad, root/rotting is for getting loot or lazy XPing, not serious XPing.
But between charming and quadding I don't think one's inherently superior. Both are very good, and I think exactly which one is better it depends on the details. What's the ZEM of the zone, what level are you/what spells do you have, what are the HP of the mobs in question, etc.
And there's also just a huge inherent difference between the two styles, in that charming is constant or near constant, while quading inherently requires breaks. So even if one is a little better or worse, you still might pick the other just because you do/don't like taking long breaks.