The Pro is the safest bet if you're going to buy a PS4 at this stage. It's not just that it does justice to your 4K TV (despite few games supporting native 4K) -- it's that many games run at higher frame rates, tout more visual detail or offer a combination of both. While few games fare poorly on the regular PS4 (Control being a notable exception), the Pro will ensure that games from this console generation perform as you'd expect. Modern Warfare is a textbook example, mating higher resolution and high dynamic range with familiar shooter gameplay.
If there's any reason to hesitate, it's timing. Sony has made it patently clear that the PlayStation 5 arrives in late 2020. You'll have roughly one year before the PS4 Pro is no longer the hottest console Sony makes. That doesn't mean that games will stop coming to the PS4 in a year's time, but it's something to consider if you intend to wring the most out of your console before you upgrade.
Buy PlayStation 4 Pro with Modern Warfare on Amazon - $300