I'd pick 5.0L over DSM any day of the week, unless we're talking about wet-pavement 60' times lol...
I have a pretty quick DSM ('90 Eclipse GSX), and it's been decently reliable, but there are plenty of horror stories. Not too hard to get into the 12s with a good driver and little money..
Gas mileage in the DSM is usually not as good as advertised. I average ~ 24-26 mpg on the freeway. I got 22-24 mpg in my notchback with 3.55 gears. about the same difference in town.
that is also with conservative driving. DSMs eat gas pretty quick (any turbo car does) if you're a spirited driver. as soon as the turbo spools, gas mileage goes to hell...
Stick with the 5.0L. they are more reliable, look better (IMHO), have greater potential for just as cheap, and are easier to work on (Changing a clutch in an AWD car blows. anything involving pulling the tranny.....
okay, I'm ranting now. Just get the 5.0L.. that Mustang you mentioned sounded nice