This one is interesting to me - I saw a thread about it here, and I recall in the gym, actually tonight, a fairly well built guy telling a smaller new guy to avoid the machines and only use free weights. Is it as simple as weight moved? Or do 'stabilizer muscles' matter, as the mags tell us?
Let's say you get a set of twins in the gym. They're 18, with identical genes, nutrition, and work ethic. You set them loose for 2 years.
Twin A is stuck in the freeweight section, where he can only use movements like Bench, military press, squat, deadlifts, rows, and dumbbell movements. He can use no machines.
Twin B is limited only to machines and cables, but just like his bro, he can use unlimited weights with it.
In 2 years, which guy carries more muscle?