Definitely different vehicles and very different drivetrains. Acura S-AWD puts a lot of torque through the front end (torque-steer is relentless) and then the rear catches up. Subaru Legacy 3.6R AWD is well-balanced and you'll never have torque steer, just "go" from both axles. I would trust the Subaru full-time AWD to get me into and out of bad weather much more than I would the Acura setup. And the Legacy will feel much lighter on its feet, and that will enhance the driving experience versus the TL. Emergency avoidance in the Legacy will also seem effortless versus the TL.
Ultimately, it comes down to how the two cars handle, drive and utilize their AWD systems, and the overall cost of ownership. IME, when gauged against each other, the Legacy handily tips the scale in its favor on all accounts. The only thing you won't get with the Legacy is a ton of whiz-bang accessories. Not important to me, but it may be to you.
- Pro amore Dei et patriam et populum -