I own both vehicles with AI3 (‘21 model 3) and an AI4 (26 model Y) for reference
The jump from 12.6.4 to v14 lite is very substantial, feels an order of magnitude safer, and has the true ‘sentience’ feel of v14. The highway feels noticeably smoother & smarter lane choices. Brake stabs are completely gone, and I had 0 issue with the sun right in its way. Yellow lights are handled much better like a human would. The brake motion is now much smoother as well, on par with my AI4. I even took it through a complex construction zone, no problems. Attention monitoring is much looser too & sensitivity is tied with your speed profile. With that said, like most new FSD updates, it had little quirks like an acceleration stab (instead brake stabs now) but it’s rare and not too noticeable. The start button & parking work flawlessly, no different from my AI4 with the same bugs that has with parking alignment sometimes. Biggest benefit with AI4 at this point is reaction time, obstacle avoidance & overall edge case improvements. Day-to-day driving is basically solved on AI3 & I’m sure will get smoother over time.
Note: if you have safety score, for some reason v14 lite gives it an error & shows it as if it was new. Small bug I’m sure will be fixed
Thanks Tesla AI 🫡