Nobody asked me but this is the best part of the fob IMO.
When I'm single in my M3P, which most of the time I am, the phone wins hands down. It's just too easy. However, when I'm with the family in the X, there's no doubt that the fob is the better option.
Opening and closing the falcons take time and it's easiest to do it while walking up to/away from the vehicle. You can feel the fob in your pocket without looking and click everything you need to. Besides, you have to stand away from the falcons anyways while they do their thing. I prefer this over digging through an app. That said, if I were single in the X, I'd rather not carry and extra fob with me and just use my phone.
The one downside to the fob for me is that I've unintentionally triggered a door opening while it was in my pocket. My advice - don't wear tight pants