Grado SR325 vs RS-1

I have a friend who just upgraded his sennheiser HD 580 to rs-2 and he choose the rs-2 over the rs-325.
I went to the store with him and have to agree with him. The RS-2 are fuller and yet even more detailed. Most important they are easier to listen to. From what I hear the only difference between rs-2 and rs-1 are the size of the driver.

Would the larger driver in the RS-1 sound better or worse than the smaller driver in the RS-2? Are either good for rock or jazz music or which one for this type of music?

I have not heared the RS-1, but Since both drivers are small absolut terms I think the larger driver would prove to sound more dynamic with deeper bass.
I think that both models will do really well with all kinds of music.

My understanding is that the drivers are the same. The difference being the part that holds the ear cup is made of aluminum on the 1's, as opposed to plastic on the 2's. Also, the 1's come in a nice box. I maybe wrong and if so I stand corrected.

My listening indicates that the RS series is not only better but they also seem to be cut from a different cloth. Better highs, deeper bass and tighter bass. I hear as much differences between the HP's and RS as I do between HP's and other manufaturers.

Go with the RS. The real question is whether the price difference between the 1's and 2's are worth it to you.

Thanks to everyone for their suggetions and I will try and go for the RS-1 probably because I buy to keep like most of us. I have gotten alot of use from my 325's and think I might be in for a real treat with the upgrade. I just hate when it isn't that much of an improvement and the money would have been better saved. I also think the RS-1 would be lighter to wear for long periods. If anyone can add something else, please do so and thanks.