Aerial Sw 12 vs Revel B 15 Subs ?

I have heard the SW12 and the B25 but not side by side so it's difficult to say which is better. However, I did purchase the B15 and it's used for 2 channel music and HT. The B15 does have a few advantages over the SW12 - $1500 less, more features and larger driver. The 3 band parametric EQ is very useful in controlling room interaction. I have the B15 crossed over at 40 Hz and it blends in very well with the Revel Studios.
It also works very well for HT. I have not heard it bottoming out yet. The most bass I have experienced is the Lord Of The Ring DVD and it didn't stress the B15.
I have had the B15 for over a year now and I am still pretty happy with it. I may add another B15 later on.

Aerial's bass is tighter, and I think it is a lot more tune-able, so its less room dependant. However, if you already have Revel speakers you couldn't do much better than matching it to a B15.

Besides potential power handling, I can tell you that the major factor here for you is going to be PROPER SET UP, CALIBRATION, AND SPEAKER/SEATING LOCATION for your bass performance!!!(far greater than any small differences in potential performance characteristics between the two!)
The Revel is going to be a better HT sub however, I can tell you that. It will have more dynamic headroom and output I believe. Also, the Revel has the VERY VALUABLE EQ ON BOARD!!!(you can put on on the Arial to be fair).
Still, getting a MUCH MORE AFFORDABLE Paradigm Servo 15 is going to yeild you the same high level performance for less!(if you're after a single woofer sub that is). You could almost get two Servo 15's for the price of one Revel B15, and put a Parametric EQ on em if you wish!...It's a thought.
Still, I'd chose the Revel over the Arial for HT/music dubties...even if you do do more music than HT. I know for a fact that I could get tremendous sound performance for music with proper set up and tweeking of the sub(that's the key to great performance from ANY SUB SET-UP!!!).
good luck

Also, you might want to consider the Earthquake MKIV 15 subwoofer! It got Stereophile's Guide to HT magazine's "platinium/sub of the year" award in jan 2003 issue. And Steve Stone said is outperformed the 4 X 15" dual woofers in his Dunlavy SCVI's!!!!(not sure about that one however). The Dunlavy's have PHENOMINALLY quick, tight, and accurate sounding musical bass on their own(4 15" drivers in sealed enslosures in a time aligned array is going to be fast, musical and highly dynamic sounding!)...so beating that is a duanting task to say the least...making his statement worth considering IMO!!!
The Earthquakes dissapear into the bottom octave when set up properly. And I've heard that from a number of "hi-end" people in this industry..including reviewers!
Good luck