LG G4 vs. Samsung Galaxy S6 vs. iPhone 6 vs. HTC One M9: 2015 smartphone specs compared

The LG G4 is a significant improvement over last year's LG G3 in several key specs, and it comes with a subtly curved design that's comfortable to hold. LG is going with plastic again for the frame of the G4, and the front looks mostly the same as the G3, but the back of the handset will offer…