P3D V6 has alot of technical improvements and that beautiful new weather engine but is it worth the hassle of basically modifiying the game files and addons to work with them. I think P3D V5 is likely the one to be archived along with V4.
I think it is better to stay with Prepar3D v5.
Prepar3D v6 is new in registry, but still using old technologies and not many 3rd party add-ons support it.
For example: PMDG and QualityWings have been discontinued for supporting P3D since v5. Therefore, v6 has very few add-ons and you may use lots of installation tricks to just fly normally.