The short answer is that phone-based presence works well for some people and not at all for others. And the zigbee arrival sensor works well for some people and not at all for others. It’s not predictable in advance, it depends on many local factors. You just have to try and see.
There are some workarounds for both the phone and the zigbee fob that can help improve things, but still doesn’t guarantee it will work for everyone at every house.
I worked with support for months trying to get the fob to work, but it just kept losing connection meaning it kept thinking I had left the house when I hadn’t. Ultimately we decided it was probably interference from the neighbors’ boosted Wi-Fi.
I ended up throwing iBeacons into the mix, and now I have very reliable presence detection, but it took a lot of work to get there.