I'm not an expert on muscle development, but to me it feels like the following:
Free weights = Individual reps have more or less identical resistance throughout the motion + gradual challenge towards the end of the set.
Resistance bands = Individual have more resistance towards the extreme end of the motion + gradual challenge towards the end of the set.
That gradual increase in resistance towards the extreme end of the motion helps build endurance/stamina (I think).
To me, when available, resistance bands gives a better workout. (But it's hard to find equivalent resistant band once you go past certain weights, that's the problem.)
Wilson BLX Six.One Tour 90. 374g, 8pts HL, SW=355 (according to TW's calculator)