Here we compiled a small features set offered by both galaxy s4 and galaxy s5
Design, measurements and weight
Samsung Galaxy S4: 137x70x7.9mm, 130g
Samsung Galaxy S5: 142x73x8.1mm, 145g
Screen
Samsung Galaxy S4: 5in 1080×1920 resolution Super AMOLED display, 441ppi
Samsung Galaxy S5: 5.1in 1920×1080 resolution Super AMOLED display, 432ppi
Performance
Samsung Galaxy S4: Quad-core 1.9GHz Qualcomm Snapdragon 600 processor, 2GB of RAM
Samsung Galaxy S5: Quad-core 2.5GHz Qualcomm Snapdragon 801 processor, 2GB of RAM
Operating system
Samsung Galaxy S4: Android 4.2.2 Jelly Bean, custom user interface
Samsung Galaxy S5: Android 4.4 Kitkat, custom user interface