Screen real estate is everything when it comes to just about any form of productivity on any platform. When it comes to smartphones, 'phablets' have become the norm as not everyone wants to carry around a tablet as well. But for those who do, the Samsung Galaxy Fold and the LG V50 ThinQ Dual Screen make for attractive options.
https://www.notebookcheck.net/Samsung-Galaxy-Fold-versus-LG-V50-ThinQ-Dual-Screen.442866.0.html
IMO an 8" screen is no substitute for a 12.9" screen during long travels :)