Well my meter gives a "sunny f16" reading on the clear blue northern sky and I get excellent exposure on Sensia 100 slide film rated at EI 100, so I'm pretty sure they can't be more than about 1/3 stop off, if that much.(posted 8261 days ago)I expose my "zones" by imaging a uniformly illuminated wall at +3 stops to -4 stops from the meter reading to give me zones I through VIII.
Why HC-110? Well, it was good enough for Ansel Adams, so it's good enough for me. More seriously it lasts almost forever as concentrate, is quite versatile wrt dilution and I quite like the look it gives with Tri-X and HP5+. I also have Rodinal and Microphen on hand. I tried XTOL and, like many others, had problems with it. You have to draw the line somewhere when it comes to stocking different developers.
BTW though HC-110 "lasts forever" my recent tests were all done with a fresh bottle.