I think what he means is that when you shoot smack, it feels more pure...mellow if you will. When you shoot morphine (enough of it) it feels like your entire body falls asleep. Like you feet and hands might, usually in my back, legs and neck. It can be quite painful and unpleasant at times. When you shoot H its just mellow and no pins and needles. If you shoot alot of H though, your vision can go along with your hearing, but its' the best damn feeling; sex x1000.
I made this comment in another post: If you've never shot morphine before, make sure your sitting down! I've had my legs collapse and the end result was getting a nice laceration and a nasty scar on my face...
Slightly graphic and NSFW... I'm only posting these to show you this is real...
http://imgur.com/9Cwd3e4
http://imgur.com/3ojv3mw