Damn did I just get downvoted for my last post? Jeez.

Anyway, this is what you get with New Vegas:
- Better RPG experience
- Better weapons
- Longer story, more sidequests
- More mods
- More Replayability
- (If playing with ENB) Better Visuals

This is what you get with Fallout 4:
- New Power Armour mechanics, Ability to customize PA
- Better animations
- Better visuals by default, Best visuals with ENB
- More cinematic feel with player voice and camera
- A morally grey story being there is no karma system
- Settlement creation

I'm not trying to get you to play FO4, OP. There are both bad and good in both games and it's subjective. If you want Fallout 4 go for FO4, if not go for FNV. I'd recommend what will give YOU the most enjoyment.

Fallout NV should not cost anymore and Fallout 4 has to go down a bit, so the easiest way is to buy both.

Because the 2 are very good and with so many mods.