I doubt very seriously hg has less metals than ug, unless ug is from china. Most hg vaccines have mercury [if not all] just to make a point. As for as hg working better, if it is as good as it was back in the early 80's then yes it is better than ug. I have tried a fare amount of ug in the last 4 years. Of course I'm 54 and that has some thing to do with my gains, but when I was 28 I had been lifting for 7 years on and off and started my 6th cycle of 12 weeks. My doc gave me d-bol 5mg 3xday
winny 3mg 3xday and
annavar 2mg 3xday
I weighed 180 at about 9% bf and could bench 180 lbs[Im 6' and have long arms] at the end of the 12 week cycle I weighed 195 lbs at 6 or 7 % bf, and could bench 300 lbs, I could military my weight. I was ripped pretty good for back then. The only sides I had was a little acne,I was still anabolic and making gains at the end of the cycle just as good as at the beginning. I have never come that close with any ug and cant even get back to where I was then. But I did have a very very high amount of mercury toxicity and was very sick for 20 years. My 2 cents worth.