4G is different than 3G. It's claimed to be faster but also consume more power. And one more concern is phone device and carier compatibility. 4G has two different kind of mobile data transmission technologies: 1] FDD (frequency division duplexing) and 2] TDD (time-division duplexing). FDD-LTE has balanced bandwidth for upload and download while TDD-LTE has more bandwidth for download.
While most 4G enable phone support FDD, only some of them support TDD and FDD. Some vendor limit the TDD band feature to regional edition and not the worldwide edition.
I think this frequencycheck quite useful to check this compatibility. You can use this as a reference before buying new 4G phone for your 4G carier.Here's some example for carier frequencies in Indonesia
Make sure the 4G band is compatible with your choosen smartphone before buying.