I'm not supercharged, but I think I have an opinion for you as I considered both before buying my current car.
The 03 Cobra is heavily underrated at the FWHP of 390, and has already been proven on dynos, in the 1/4 mile, and at the track with very few mods. You will break into the 11's with very few mods, and the price is right at $35,000 for a coupe. However, alot of dealers are inflating the price to astronomical levels so it may be hard to get it for the advertised MSRP. Do a search at
www.autotrader.com I found one a dealer was selling for $50,000
The S281E is the new supercharged Saleen Mustang, the plain S281 is not supercharged. The S281-Extreme has been advertised with a FWHP of 425, but I have yet to see any tests on dynos or in the 1/4 mile online or in magazines. However, the body kit of a Saleen to me has a much more desirable look to it than a Cobra. Also while the Cobra holds a certain spot in the pubics view of being a rarity and highly sought after car, the Saleen has an even stronger reputation of this. The biggest difference between the 2 will probably be the one affecting your check book. The base MSRP of just a regular S281 non-supercharged Mustang is $37,000+ for a coupe, I would guestimate that you could probably expect to pay at least a base MSRP of $45,000+ for a S281E coupe. Saleen's actual website may have more of what you would like to know regarding this car
http://www.saleen.com/
So to me it basically comes down to this can you get a 03 Cobra for the advertised MSRP, and is Saleen also underrating the FWHP of the S281E as SVT is with the Cobra. If not, then they may be very close HP-wise and the main difference would be the look of the cars and possibly the cost. That's just my $2.00 worth on the subject lol
Who here drives an 03 Cobra or supercharged Saleen? 
