With respect to TACC, I leased an AP1 model S90D and was very comfortable with auto steer and TACC in it so that is my vehicle for comparison purposes. I own a 2017 Subaru Outback touring. The binocular camera based TACC system in the Subaru is FAR superior to the TACC in my AP1 Tesla. Much smoother and recognizes many more difficult response situations. The lease rate on my Subaru is also 1/4 of the lease rate on the Tesla (-; . Working AP, not just TACC, is a gating issue for me to get another Tesla. Until it is fixed I will wait.
I'd be a little careful trying to declare a winner between two very different types of implementations.
The AP1 Tesla TACC is a predominately radar based implementation. So it comes with some benefits, and some caveats. One big advantage it has is it can see two cars ahead. So if the driver in the car 2 cars ahead slams on his brake it can start to slow down before the driver of the car in front of you even reacts.
The radar aspect of it does have limitations especially with stopped cars, or mostly stopped cars. It doesn't see them all the time. It also can SOMETIMES react in a corner to the car in the other lane.
In my overall experience with TACC on AP1 I'm pretty satisfied with it's smoothness. Mostly it comes down to the setting used, and how the driver in front of you is driving.
It doesn't recognize difficult response situations because it's not supposed to. I'm not exactly sure what you're referring to as we're only talking about an adaptive cruise control system. A lot of us including myself don't want it to do too much.
The Subaru system is a stereo camera only solution. It likely has some strong advantages of not reacting to cars in the other lane. It's main drawback has to do with relying on vision. So it's ability to sense will be compromised in some situations (bright sunlight, rain, dirt, etc), and the older versions have been reported to falsely react to shadows. The one on the 2017 is pretty refined though so it should be pretty solid.
I'm not sure how it can possibly be smoother than AP1 since it's attached to an ICE car that's pretty sluggish (no smooth torque). My mom has a 2017 Subaru Outback with the system so I have experience with it. It's a pretty nice system especially for a $30K car. I personally never experienced any false braking situations, but I did experience some false warnings as I do with my AP1 Tesla.
My main dislike with Tesla is they don't even you any control over the various aspects of the system, As an example it slows down in corners as if I'm driving miss daisy. There is no way for me to tell it that I take corners at 10 over the advisory speed if not higher. To my knowledge the Subaru system doesn't do this, and if it did they would have some button for it. Subaru has buttons for everything. Button after button after button. God it took me forever to explain to my mom what all the buttons did, and to say when the dash indicator was on it meant the system was off. We also have this major battle over the lane departure system. I turn it off, and then she turns it back on. I turn it off because it's horrible pile of crap system. I turn it off in the Tesla as well since it's horrible.
The only thing I really disliked about the Subaru system was it could be a little annoying at how much it beeps at you (anytime someone gets in front of you or exits), but I believe I can turn this off. If it was my car I would. But, I haven't really had a good chance to full vet the Subaru system because my mom ruined the car. She did so by getting a State Farm driver quality measurement device installed in it (she wanted cheaper insurance). She also won't let anyone switch it away from the Elvis radio station on Sirius XM. She's under the impression that she'll lose it since she never paid for it, and it expired awhile ago.I keep telling her that no that's not how the system works. But, no she doesn't believe me. So no one can switch it or there is hell to pay. If you love Elvis and you don't mind state farm evaluating your driving based on an accelerometer then it's a great car. Well for an ICE car that is.