i used it, and pain is just a word, i swear that shit was terrible, but for some reason, after the first 5 shots in each site, it got a bit less, then they didnt hurt at all. I guess my body adapted. Very nice product if you can find it.
id say sust may be a little better cause lower aromatization, plus sust has 250 mgs percc, as compared to 200. Also im sure sust hurts less, as do dull 18gauge needles.