The Year Matters.....kind of. The original poster did not say..
Here is my take, including input from from talks with the old Team Viper, and it still rings true:
A 3.73 causes a 21.5% increase in average RPM of the trans output shaft and rear end components over its lifetime. This excess wear and especially excess HEAT should be considered, especially on cars that are tracked on roadcourses.
A differential cooler is almost essential with 3.73. Coupled with the massive wheelspin that can result in 1st and 2nd with a 3.73, a 3.55 gear is a better overall choice, with a more manageable 15.6% rpm boost. And, the steeper the gears, the more whine is likley to occur.
A 400 HP Gen 1 car is more civilized with a 3.73 than a 450HP Gen 2. But exit a corner even in a Gen 1, and be VERY CAREFUL with adding throttle slowly. Mash it = Smash it. And any car pushed on HP exagerates the "gain" achieved with gearing.
3:45 is a 'niche' gear loved by frequent quarter-milers becasue it does not require a shift at 1300' like the 3:55 might. If you drag race passionately and frequently, choose 3:45. Rare, usually less strong, and more costly. Equal cars on the STREET, a 3:55 will knock off the 3:45 handily.....
If you have 600+ HP or esp a S/C, choose 3:33. Can be a difficult unit to find, and should definitely be cryo-hardened first.
Those with gear swaps should consider the trans and rear end oils in a "Severe Service Cycle" change interval. Dont Forget Those Out-Of-Sight Lubes !!
