This comes around fine.
Wait, what? That's one hell of a weird change.
Personally I thought a big issue with Fallout of Nevada was the fact they stuck with the clearly unbalanced SPECIAL of FO2, when current modding capabilities would easily allow them to change and rebalance it, thanks to SFALL.
But making Small guns be pistols and SMGs while Big Guns are now rifles and shotguns is rather strange and atypical.
Did they change anything else? And where the real big guns are placed now?
Sonora has more "realistic" (in classic post-apo sense of the word) roster of enemies - no supermuties, guys in PA, deathclaws and heavy robots; most enemies are rather soft. Thus, low-level guns stay valid till the end and really big guns are rare (yes, they still covered by big guns skill). The game is perfectly finishable with small guns since some pistols are really powerful.
If anything, this helps to bring more weapon variance since let's admit that, there are little reasons to use pistols in vanilla Fallouts where you can almost always be better off with a rifle. Here, you can have a proper pistol build; heh, this is what I did at my first playthrough, actually.