I've had a motley band of instructors over the years. Two particularly bad ones stand out, and they were both hour-collecting towards their right seat jobs. The time spent with them (not much of it!) was totally wasted.
I've flown with young instructors with fewer hours than me, and found it a very fruitful experience - I think sometimes we taught each other a few things.
I had an outstanding young instructor at NAC a couple of years ago, for the FAA IR. I think I had more hours than he did, but he was in a different league: he knew it, and he could teach it. A real joy to fly with!
I probably learned most, early on, from two or three relaxed blokes who'd finished their flying careers, and were instructing for the love of it.