I also still have trouble picturing Los Santos being any larger than Liberty City.
All in all, GTA V's total land surface is only 35% larger than 3D San Andreas'. Though we all know how that turned out with GTA V, where the map was supposedly bigger than San Andreas, New Austin, (RDR 1) West Elizabeth as well as Liberty City all combined together. Turns out Blaine County is being composed of 50% mountains which serve as nothing but fillers and that Rockstar forgot to tell us the statement included the surrounding explorable waters. Rockstar always markets their new game worlds as being their biggest and most ambitious to date.