Not sure if there will be any feature comparison for minor upgrades like Pi 1.2 vs PI 1.4.
As these are incremental releases which doesn't introduce new feature but have bug fixes and new Device and Software Supports.
You can also look at Quick Start Guide for these PI versions and would hardly find any new features.
Key Feature PI 1.4 Vs Key Features PI 1.2
I compiled the excel sheet which has the Key features and you'll not see any difference (Find Attached).
Most basic feature comparison is what you have already mentioned. Release notes where it describes all new features this release introduces.
PI 1.4 was majorly targeted to support .11ac in newer AP platforms such as 36xx etc.
The following features and enhancements are the highlights of in Cisco Prime Infrastructure 1.4 apart from what it can do similar to PI 1.2:
•Management Support for WLC Release 7.5 •Support for 802.11ac Module •Support for Cisco AP 700 •Policy Classification Engine •Detect Dead Radios •FlexConnect Audit Support •Autonomous AP Support •Client Stateful Switchover (SSO) •Cable Modem Monitoring •Support for SFTP