This is all anecdotal, so take it with a grain of salt. I'm on gear, and it made it so I could workout harder, longer, and be back at the gym the next day. I have pretty good proportions for squatting, I'm 5'7" and carry a lot of mass in my legs, and my coach basically wanted to experiment on me and see what we could do with my squat.
A few weeks into being on gear, (It was just a test-e cycle with a 4-5 week dbol kickstarter) he pu tme on a squat program when I was doing high rep, relatively high weight, pause squats 4 days a week. It would be like 5 sets of 15, 2 second concentric, 1 second pause, 3 second eccentric. It was fucking brutal, and I might hobble to my car a little, but the next day I was there all over again.
In 3 weeks my squat went up 50lbs. Like I said, on gear I could train harder, longer, and just better. Yeah it increases muscle growth, but a big plus is that it increased my recovery time, and how much I could put into a single workout. I was training like crazy.