Why? you ask... well the road to work is 60 mph so I avg 65-70 on it, 3:73s allow me to use 5th where I just barely couldnt before... the road is twisty with lots of small and one VERY steep hills/hill. My gas went up from 220 a tank to 260 just from that 8 mile stretch. Driving like an ass I still have a gain of 15-30 miles per tank. NOTICE: I've only gone 3 tanks of gas so far and havent got to romp on the tranny yet, though I plan to this week when I fill up the 4th time. Do I wish I would have gone 4:10s? Definately, but I'm glad I didn't, as a DD car and with a S/C or Turbo in my future I'm happy with the minimal performance gains, but I can definately imagine the POV from the 4:10s or bust crowd. Also notice I havent got to romp on the gears, so I expect the daily driving gains to cut down to about 10-20 miles per tank, and I expect there to be losses on miles per tank when I romp a full tank. The lowest I have managed was 110 miles on a tank with stock gearing btw, the average assinine driving results are closer to 180-200 on a tank. Either way, if you have the money and are unsure I say 3:73s first. If you dont have the money, definately 4:10s... I rode in cars with 4:10s before deciding on my pruchase and they felt fun as fun can be from the pass. seat.
*EDIT* I forgot to mention my gains/losses are not scientific as it being winter on some days I have had to warm up the car for extended periods of time due to frosty windshield etc...