If you have a decent graphics card (6GB vram+) you will definitely see a difference regarding fps and overall perfomance. P3DV5 also uses directx12 and bring some new futures such as EA (enhanced atmospherics). Most of the airport for p3dv4 do work for p3dv5 and many have already received an update from their devs. If you are planning to buy V5, I would suggest you wait until MSFS comes out (2 weeks for the beta).
Personally I'd go for V5 but yeah, like the other commenter said, msfs 2020 is probably better suited for your money if you're deciding to purchase it now