Z3 on the stretching bank. Acer has refreshed its entry-level devices, and places a four-inch smartphone with dual-SIM feature between its Z3 Duo and Z5. Their specs are very similar. The most interesting innovation is surely the Custom Profiles, which are to make the smartphone easier for newcomers to use.
http://www.notebookcheck.net/Acer-Liquid-Z4-Duo-Smartphone-Review.117264.0.html