What was that better car with and system if you do not mind me asking? Torsen rear end with a Getrag 6 speed and equal length drive shafts for near perfect front to rear tow and yaw control with a fully locking differential with control through a DCCD is about as perfect an AWD setup that you can ask for in any AWD vehicle.
From a handling perspective. I found that both the S4 (with the sport differential) and the Evo beat the STI. I tested by coming to a complete stop on snow, cranking the steering wheel all the way to one side and flooring it. The STI just plowed mostly forward with significant understeer (regardless of DCCD mode). The S4 was able to whip the rear end out and oversteer nicely. The Evo did the same. I do ice racing in the winter, so this is important to me.
I chose the Evo (though it was a hard decision between the Evo and S4).
From an engineering perspective, the Evo’s front differential is more or less the same as the Subaru. Despite what Subaru owners think, there is no torque steer and it does have equal length axle shafts. (WTF is the point to Subaru’s “Symmetric” AWD??)
The center differential on the STI is a bit different than the Evo. I have found that the Evo’s is much more responsive and able to change torque split in an instant. However, the STI’s DCCD is still decent. I have taken both apart and definitely prefer the Evo’s.
The Evo stands out once you get to the rear axle. The active yaw control can transfer 100% of torque left or right. It does this with hydraulic plates on top of a LSD, kind of like the GTR rather than by using the vehicles brakes. The algorithms that control this are superb and give you limitless control in a skid. The Subaru rear differential was just a limited slip. It had the ability to apply brakes to get some sort of yaw control (Subaru was just being cheap with this) but it’s a night and day difference compared to the Evo/S4. I hope Subaru upgrades to a real AYC system..
I’ve been ice racing for 4 years now and have yet to lose a race to a Subaru (though I’m sure there are some better drivers out there that could beat me in their Subaru’s or maybe I just need to race more).