My belief is if there is such an obvious difference in vibrate characteristics between phones of the same model, then one is more likely built to desired specs than the other. I choose to consider the one out of spec to be bad or defective but I guess you can argue semantics if you really want to. Regardless, I don't like the rough vibrating one and prefer the smoother one, especially since Motorola doesn't let you adjust intensity. That's one thing I like about the S4 and G2. Why don't they do this anyway, is there a patent on it that they are too cheap to pay? Are they using a part that doesn't let them adjust it? I find it really strange after all these years that they continue to choose not to provide this feature which I think is so basic.