FSD Beta is more capable than the current AP. But I am not sure which is more reliable. FSD Beta does make some of the same mistakes that the current AP does, like trying to center itself in the middle of the lane when it is supposed to bias the left lane. FSD Beta also makes new mistakes like missing left turns. Also, FSD Beta will be used in many more scenarios which will require more driver attention. The current AP has the advantage that drivers probably won't use it very often on city streets since it is less capable. I know I rarely use the current AP on city streets. But owners will use FSD Beta more on city streets so they will need to be more vigilant.
Here is a video that shows a bunch of problems with FSD Beta. Some of them are minor driving policy issues but some of the issues could potentially be very unsafe. When I see FSD beta almost hitting parked cars and missing turns and almost hitting stopped cars in the incoming lane, trying to go straight when it is in the turn lane, or trying to go through red lights, those are more serious and it makes me skeptical that FSD Beta is ready for wide release.
Go to 14:12 for the bad cases.