The issue I have with the phone vs. the fob is, it's a multi-step process to open the frunk, or open the trunk (when the car is locked), when using the phone. My typical use case: when bringing home takeout, I always put the food in the frunk to keep from stinking up the car. It's very easy to double-tap the fob in my pocket, without looking, to pop open the frunk. On the 3, I have to pull out my phone, open the app, then tap the button. Use case for the trunk: when I'm standing away from my car, and someone else needs to access the trunk, I can just open remotely, again, without looking or taking the fob out of my pocket. With the 3, same problem, I have to launch the app to open the trunk, and it takes a couple extra taps.
Ok, yes, I know these are minor inconveniences. But I really wish they offered the option of using a FOB. When Summon is available on the 3, doing that action with a FOB is much easier than using the phone, in my experience with the S. And in that scenario, I want instant and reliable response, I don't want to worry about the phone connection being flaky and not stopping when I want it to.