I've run them both for extended periods and done blood work on both.
The Mk677 certainly increase the igf-1 levels , made a big increase in appatite and greatly Improved sleep , but it also had a marked increase in faster morning blood glucose levels , the lathargy lasted a long time and it causes ALOT of water retention.
HGH raise the IGF-1 levels significantly , didn't seem to effect appatite at all , sleep improved when it was taken before bed. It also had a noticable increase in faster blood glucose but not as bad as the MK , no noticable lethargic feeling and way less water retention. There was also a noticable amount of fat loss and decent increase in training pumps.
Dollar for dollar I'd chose good generic HGH every time