I never heard the RS-2, but I used to concurrently own both the RS-1 and MS-Pro. Here is a cut and paste from a comparative review I wrote a while ago...
INTRODUCTION
I’ve been comparing the Grado RS-1 (#26xx) and the Alessandro MS-Pro (no SN) for several weeks now and would like to describe, as best as I can, some of my observations. I initially bought the MS-Pro and really liked it. However, I was very curious to hear the infamous RS-1 in my current system and decided to get one to do a head-to-head comparison.
HEADPHONES
Both are “fully” burned in (at least 120hrs on the RS-1; much more on the MS-Pro). For those who don’t know, the MS-Pro is a rebadged “variant” of the RS-1 made by Grado. The MS-Pro lacks the wooden buttons on the metal grills. The MS-Pro has a walnut (brown) colored finish while the RS-1 has a more “honey” color. It is not exactly known how their transducers differ.
Only stock bowl pads were used in the comparison on both cans.
Associated equipment
CD transport: Music Hall CD25.2 (internally dampened with Dynamat Xtreme, Sorbothane, and Blu-Tac); placed on Townsend Audio isolation platform
D/A converter: Ack! dAck! v2.0 (with high output option)
Amp: Headamp GS-1
Cables: Ack! Industries The Digital Connect digital cable; Kimber Silver Streak IC; power cords: VH Audio Flavor 1 (transport) and Volex 17604 with P&S plug (amp)
I'm not expecting to get too many comments from wiseguys who readily dismiss headphone opinions because they think the user's amp and/or source is inferior.
METHODOLOGY:
Only well recorded store bought CDs (mainly classic rock and some jazz) were used for evaluation (no MP3!). I would listen to a portion of a track several times in a row and then quickly switch cans and note the differences I hear. The dual output jacks of the GS-1 allows both cans to be plugged in simultaneously, greatly reducing the time between switching.
Note:
All comments are only in relation to the other headphone.
RESULTS:
Soundstage: This is the most notable difference between them. RS-1 is much more forward and has that in your face quality. MS-Pro is quite laid back. I found the RS-1 soundstage to be relatively flat and two dimensional. MS-Pro has a much better sense of depth and separation between instruments in the depth plane. Width appears to be similar.
Bass: The RS-1 definitely has much more bass that tends to exhibit a “boomy” quality. I actually found the bass to be too much at times and had to adjust the tension on the headband so that the bowls are as loose on my head as possible. The MS-Pro bass is less abundant but much more tight and accurate. During the beginning of U2’s
Bullet the Blue Sky, the kick drum sounds more tight and “real.”
Vocals: RS-1 has a fully “body” on the vocals. The MS-Pro tends too sound a little thinner, more distant, and more "echoey" on some recordings, especially those with an inherently laid back midrange. On Frank Sinatra’s
Fly Me to the Moon, this is quite noticeable. You can hear this trait on the RS-1, but it is not nearly as noticable.
Guitars: MS-Pro reproduces the “twang” of the guitar sound more accurately. RS-1 sounds a little “rounded.” On the Beatle’s
Yesterday, the acoustic guitar sounds more real to me. The “body” of the guitar is reproduced better on MS-Pro.
Cymbals and snare drums: On Steve Winwood’s
Higher Love, MS-Pro has much more “air” and spaciousness with well-reproduced decay. RS-1 sounds noticeably duller and closed in.
CONCLUSIONS
With the above noted differences, I actually had the
hardest time deciding which of the two I liked better. The MS-Pro has a more "live" sound to it than the RS-1 due to its more spacious sound and decay. Diana Krall's
Live in Paris sounds, well, more "live" with the MS-Pro. The main liability with MS-Pro is the somewhat thin and distant vocals on some music and the less than impactful bass. I eventually decided that I favored the RS-1 because of it’s more forward, aggressive, fuller bodied sound over the more “accurate” and “realistic” sound of the MS-Pro. The RS-1 to me was more of a contrast to the Senn 650/Zu that I currently own, which is the reason I decided to purchase a Grado product in the first place.
COMMENTARY ON PADS
I tried reversed bowls on both cans. I even forked over $35 for the highly regarded TTVJ flat pads. It seems like you can't mention anything about the sound of Grados without someone shouting "TRY FLATS." With both rev bowls and flats, I found the sound to be too muffled. The bass became too punchy and prominent, kind of like turning the subwoofer volume way up in a HT system. Not only that, they were really uncomfortable, especially the flats! I could not wear them for more than a minute. The stock bowls feel and sound much better to me. It is important to note that I have small and flat outer ears. The bowls completely envelope them to form a near airtight seal. This likely is why the bowls work the best for me. Also, even brand new, I have no issues with the bowls being itchy and I happen to have sensitive skin.
It is worth mentioning that ever since I wrote the comparative review, I crushed the bowl pads on the MS-Pro under some heavy books overnight. This has the effect of bringing out the bass and midrange to near RS-1 levels, likely because the drivers are closer to the ears. Unfortunately, I did not do a direct crushed bowl MS-Pro to RS-1 comparison because I was "forced" to return the RS-1 due to financial reasons (unexpected loss of job). The MS-Pros were already bought and paid for before I did the comparison. To this day I'm still really enjoying the MS-Pro and have no urge to upgrade as of now. However, I might change my mind after the upcoming Bay Area meet. 
