The Gaming 3 has 8 power phase, the Gaming 5 has 12. This is likely an important factor with Skylake's granular overclocking features. The gaming 3 has fewer SATA ports and there are a few other minor differences as well. If you don't plan to run many drives or do any serious overclocking, the Gaming 3 is probably fine. Gaming 5 just has a few more features and better power phase.