I like that we have all three options.
Phone as key is what I use 99% of the time. It works great. And I almost never go anywhere without my phone anyway, so by combining key with phone it's one less item I have to remember to bring with me.
The big problem with the phone is that phone batteries don't last very long so you're at risk of getting locked out of your car if your phone battery dies. And that's where the key card comes in. I would not want to use the key card everyday, but it is a great backup. It is easy to keep one in your wallet so you'll never get locked out (unless you happen to you lose your wallet on the same day your phone battery dies).
The FOB is a nice compromise between phone and key card. Just as easy to use as phone, but no risk getting stuck because of a dead battery. The only downside is that it's another thing you have to keep in your pocket/purse. But if you are willing to leave your phone behind the FOB takes up less space than a phone.
The FOB can also do something that you can't do with your phone. Open the front trunk. Yes you could unlock your phone, open the app, and find the front trunk button, and then click confirm when it says are you sure. But that takes forever - it's easier to just open the door and touch the button on the screen. If you have the fob, all you have to do is click the frunk button.