if you want to keep it for 3-4 years then get the 1600, the 1500x is a very good chip nonetheless, I just see games using more cores the next coming years. i5's are already running 100% in more recent games and the 1600 just has more headroom and potential due to more cores and threads.
You're probably going to hit the highest clocks with the 1500X, which is what matters for some games now. However, the 1600 might be better if newer games start utilizing more than 4 cores.
if you want to keep it for 3-4 years then get the 1600, the 1500x is a very good chip nonetheless, I just see games using more cores the next coming years. i5's are already running 100% in more recent games and the 1600 just has more headroom and potential due to more cores and threads.