I drove a handful of driver assistance vehicles before buying my Tesla. To be honest, I wasn't that stoked about buying a Tesla, but the way the system worked for my commute won me over. My commute is a 90-minute mix of 2-lane roads and 6-lane highway, with plenty of curvy roads and mostly good markings.
1. Audi A6 (not the new A8 L3) Designed for freeway travel. We couldn't get it to engage on city streets. Wouldn't operate below 30 MPG.
2. Honda Adaptive Cruise/Lane Keep: Also designed for freeway. Kept the lane well. Wouldn't operate below 30 MPG.
3. Volvo: Dealer was really excited about new system. Really spotty engagement on city streets. Literally ran us off the road without warning. We tested a couple of times in the same spot, same result. Salesman was really disappointed.
4. Mercedes adaptive cruise and lane keep (2015 vehicle): Rudimentary, but effective. Does not like turns, mainly good for staying in lane on long straight freeways.
5. Nissan Pro Pilot (2018 Leaf): Kept in center of lane better than any vehicle tested. Solid, confident feeling. Requires a cruise "resume" after every 3 seconds of stop time when in stop and go traffic. Asinine design decision crippled what seems to be an otherwise competent system.
6. Tesla (Model X, AP2, 10.4): Worked with high confidence on city and freeway streets. "Just works" brilliantly in stop and go, including a relaxation of "hands on" requirements during extended periods at low speeds. Has a strong tendency to ride the left side of the lane, which is unsettling on 2-lane roads. Intuitive interactive design. Still doesn't handle the sharpest clover leaf on-ramps and tries to drive through the middle of roundabouts.
All told, on my 90 minute commute, I have to intervene maybe 5-6 times with the Tesla, which was much better than competing systems. I could do without all the accouterments of a high priced vehicle, but for self-driving Tesla was a clear winner. If not by sophistication of their system (Nissan feels more capable), then by Tesla's smart implementation and design decisions for the feature.