It is my understanding that all the ISM saddles are the same width at the nose,
it is the taper towards the back of the saddle that is different. I believe they are all 55mm wide at the nose.
They've re-labeled all the models for 2016, describing them as "Performance" Long, Short, or Narrow. The Road/TT are 'Short', the Prologue and Podium are 'Long', and the Attack/PN series are "Narrow'.
The Attack and the Prologue are the same length, but from the nose the Attack doesn't flare out as much. Models like the Road and Racing are short in length, and flare out 'quickly' to the widest part.
Dave is somewhat right is sticking with his recommendation that placement is everything. On the 'short' saddles it's easy to sit too far back - the Attack was designed to give more clearance for the thigh, but you should still be sitting pretty far forward. Not to have your legs sawing up and down on the widest area.
ISM and SMP are philosophically the same in that you are supposed to be resting the 'face' of the pubic rami on the twin noses. If the ISM's are just too much junk up in there, but the SMP Stratos is too much the Pelvic Protector, the SMP T4
might be a good middle ground for nose width at 47mm.
Now, I am not taking into consideration other factors such as stance width and pelvic rotation. Post pics or feel free to pm me for email.
FIST/SICI/FIST DOWN DEEP