XZ1 has, RX100 don't
I like the RX100, but for the types of photos I take, it just doesn't cut it. These are the features I like about the XZ1:
1. Ability to use remote control.
2. Ability to use auxiliary lenses for digiscoping, afocal coupling to microscopes and telescopes.
3. Flash hot shoe
Just because the RX100 has a BIG sensor, does not mean its great in other areas; if you catch my drift.