Depends on whether you're talking about auto or manual vehicles. The autos typically have a slightly taller rear end... Forester and Impreza RS autos have the 4.444, manual versions of those cars have a 4.11. Legacy manuals have a 3.90... make sure you don't mismatch final drive ratios by mistake, it can get expensive.

Of course on the flip side, if you swap in a USDM WRX 5 speed, you can keep your rear diff, as the ratios are the same. The WRX has a 3.90 front diff, a 1.1:1 center stepdown ratio, and a 3.545 rear end.