I have heard great things about Butch Harmon. Phil Mickelson is my favorite pro golfer.
Not sure about lessons from Sigel or Earl. I wouldn't assume their playing skills are equivalent to their teaching skills. I've heard that a lesson with Earl is more like a personal exhibition where you get to see up close just how awesome he is. I would want to ensure that my instructor is good at spotting stroke flaws and flexible enough to recognize whether or not such flaws are actually creating a problem. I wouldn't pay an instructor to give me basic lessons on pocketing balls and how to move the cb around the table for position -- this is basic stuff that can be found in many instructional books already.
Your choices are your choices. These are mine for my reasons.
Sigel plays great 14.1. I'd like to learn how he reads a rack and how he thinks his way around positioning the CB on each shot to keep it going, and going and going.
There is no instructor out there who can teach what Sigel knows because they can't do what he does or know what he knows. They don't have the EXPERIENCE and SUCCESS, or KNOWLEDGE.
Earl was a great 9 ball player as was Sigel. I could go with either or both of them primarily in planning an entire rack out after the break and deadly safeties.. Earl for entertainment value also.
I have no reason to believe pool instructors are any different than school teachers or any other lesson givers out there. Teachers often get settled into their own bias opinions about how something should be taught or done, like the the stance or aiming when playing pool. So I'd choose my teachers wisely, based on who I think can help me with my needs, not based on popularity or an impressive row of trophies.
It's not just about teaching and where there's a big disparity in a school teacher. A GREAT instructor has to be a GREAT diagnostician like a GREAT doctor. If they misdiagnose the real problem and start treating it for something else, the patient is going to get worse and maybe die.
I wouldn't want an instructor who just teaches the same curriculum to everyone. If I want something specific of my choice, then I'll seek a SPECIALIST in aiming, banks, diamond system, etc. Very few instructors are great diagnosticians. They misdiagnose more times than not or throw out band aid fixes.
I'm sure I could give you great guitar lessons. And if you advanced quickly and decided you wanted to pursue jazz improv or percussion finger style, I would put you in touch with someone more in tune with that genre of music, like my buddy Spencer, who is self-taught, here:
https://youtu.be/ZAxK1z-BUUk?t=45s