My RS1s came with bowls so I figure that's the way they were meant to be used. My 225s came with flats, tried them for a couple of days then got the dealer to swap them for some bowls..much better IMO.
I've always thought the Grados are very sensitive to source and recording, (maybe more so than Sennheiser)because they place you so upfront.
Going from an Arcam 7SE to an E-Sound cdp made a world of difference. I still have some recordings in my collection(mainly cds) that dont sound very good on the Grados but they generally dont sound great on my other phones either.
There are too many poorly mastered, compressed, or low bit rate recordings around and too often their faults are blamed on the phones rather than on the source where it belongs.
This statement holds true for me aswell. The reason I prefer the bowls over the flats is because of the Apollo/Mad Ear+ HD2 combination. The Apollo being a warm cd player + the sweet warm sound of tubes makes the RS1 sound fantastic with most music thrown it's way.