I suppose it depends on your priorities and what you like about the franchise. NV is basically Fallout 4.25 in terms of gameplay, but it definitely has the best writing and quest design of any of the 3D games, possibly the entire franchise. FO4 has some huge gameplay improvements, the settlement system (which I personally don't like, but you might, and it's easy to mostly ignore if you don't) and of course it's much prettier, but the writing and quest design are easily the worst of the series and most of the RPG crunch has been removed.

I liked FO4 and have about 70 hours in it, but I'm not really feeling inclined to ever go back and finish it. I miss the stronger RPG elements, so I find myself going back to New Vegas instead. But in any case, I hope you have fun with whatever you decide to play next!

Fallout 4 is a direct sequel while NV is the continuation of the old Fallouts, before Bethesda did a complete reboot. So while it is a great game (in several aspects superior to FO3/4), it will still a little bit like watching an old Star trek movie in-between the two J. J. Abrams reboot ones. same franchise, but totally different styles.