I actually prefer energy weapons on very hard. Nothing can survive a sneak attack head shot from the Y186 with max charge ammo, and nothing else will survive the plasmahose(plasmacaster) in medium/short range. Max charge ammo is the real addictive drug in FNV.
It really comes down to this. Guns are more prevalent, and if you are new to the game, or not huge on item hunting, guns will generally be easier to play with. They are more abundant, and they have a natural knack for punching through DT- which is extremely important against tougher enemies. You can get around DT with energy too, it just takes a plan, you need to know what guns you need, and how to get them ASAP.
Once you have a gauss rifle and plasma caster with a pile of maximum overcharge ammo, energy weapons becomes very powerful, but until that threshold they are tough to use against anything with decent DT.