If I compare Asus Zenbook/ Zenbook Flip and Asus Vivobook then the first point of difference is the specifications. Asus Zenbook series is incorporated with high-end hardware as compared to Asus Vivobook. Asus Zenbook series has a higher price as compared to Vivobook. But personally, I would recommend going with Zenbook, if you want good display, features, looks, and speed. Zenbook flip is equally good but with a slight difference that its screen can be adjusted according to the user requirement.
Few best options available in Zenbook are:
-ASUS ZenBook 13 Ultra-Slim Laptop
-ASUS ZenBook UX430UA
-ASUS ZenBook UX303UA
Dell Inspiron 13 5000 is also good enough comes with a 2-in-1 design. It has a good processor if compared to the above options.
If you want more insight to this quation then you are requested to be more specific to the choice of the laptop.