No Mutants Allowed has gathered together comments from different forum posts by project leader J.E. Sawyer, of particular interest is a long explanation of the changes in weapon skills.
In 1997, I played the original Fallout. Like the games that followed it, Fallout had Small Guns, Big Guns, and Energy Weapons. In F1, the gun skills were designed for phased obsolescence. If you tagged Big Guns or Energy Weapons early on, you would not be able to gain much, if any, benefit from it for a long time. Even back then, I thought this was problematic. Before playing the game, players could not know how content would limit the applicability of weapons. Ultimately, it came down to three weapons: the minigun, rocket launcher, and flamer. Large, with heavy ammo, and either burst or AoE only. In Fallout 3, the list of Big Guns was expanded to include the fat man, rock-it launcher, and gatling laser. In most situations, these weapons were all still at least mid-power at their weakest. In talking to people in person and online, and in reading online commentary, I found that people were also still unclear on what marked the clear division between Small Guns and Big Guns (and even Energy Weapons, in the case of the Gatling Laser). Certainly the UI could be improved to help with this (something we have already done for F:NV), but it conceptually was a sticking point.
When I was looking at Big Guns for F:NV, I considered that the list of weapons was small compared to any other weapon category and several of the weapons arguably belonged (or at least could be easily categorized) elsewhere. Moving the Big Guns to different weapon skills and dissolving the Big Guns skill would allow weapons like the minigun to remain as a powerful top tier weapon without needing to invent low-tier "Big Guns" that might further confuse the dividing line. Coming up with a wide power spectrum of Guns, Energy Weapons, and Explosives would not be hard at all. Since our skill point economy is more frugal (I'll delve into this another time) and since we do have Strength requirements on weapons (resulting in increased sway for firearms and a decreased rate of fire for melee/unarmed), where you invest your skill points and SPECIAL points is still pretty important. A fully upgraded minigun wielded by a character with high Guns and high Strength cuts down rooms of people like a scythe, even at relatively long range. In the hands of an unskilled, low Strength character, it sprays a lot of bullets all over the place.
The exact categorization of weapons in F:NV isn't rooted in the logic of transferable skills from real life, but it's arguable they never were previously, either (missile launcher/flamer/minigun, for example). The categorizations have more to do with being clear and consistent with definitions. It follows this basic pattern:
* Does it explode? It's an Explosive.
* Does it use Small Energy Cells, Microfusion Cells, or other energy ammo? It's an Energy Weapon.
* Does it use conventional bullets of some flavor as ammo? It's a Gun.
So while it's accurate to say that Big Guns no longer exists as a category, it's not accurate to say that Big Guns and Small Guns were combined. The weapons in Big Guns were divided among the other weapon skills.
I know not everyone will be happy with this re-organization, but those are the reasons for the change. I hope the reasons are clear, even if you disagree with the decision. Thanks.