We've got a Greenlee 2011 that works very well.
Even on large distribution systems where you'll have several "levels" of distribution panels feeding each other.
But you've got to watch the video that comes with it a few times and get some practice. Holding the unit the right way, using high and low sensitivity correctly, and especially how to handle grounding at each end of the circuit make a big difference. Once you know what you're doing, it's pretty easy to narrow down the search and focus in on the right panel and then the right breaker.
The first few times I used it, I discounted it as junk. Then one day I really needed it and watched the video. It worked once I knew what I was doing. I use it all the time now.
I don't know that it's the best since it's the only one I've used but I'm satisfied with it.
