P3D v3 is 32 bits, just like FSX.
No matter your operating system and no matter how much RAM you have on your computer, it means the simulator is not able to use more than 3,2 Gb of RAM, which is quite a low amount of memory by nowadays standards.
Because of such a low limit, the simulator can run out of memory quite easily when it uses too much addons or the settings are too high.
When there is no more available memory, then the simulator crashes, even though it was still running with good FPS...
P3Dv4 is a 64 bits application, just like Flight Sim World and XPlane 11. It means it can use up to several terabytes of memory, not just 3,2 gigabytes.
This means it will not run out of memory so easily anymore, which means it will allow much more detailed addons. And I'm not referring to just graphical beauty, it's also about the amount of features, complexity etc...