Also voting for smaller maps, and my reasoning is similar to some other folks above:
Manageability for the designer
It's easier to juggle events if they're localized in smaller maps. With a large map, you either have to do a lot more juggling with a high quantity of events, or you simply have to minimize the number of events. With smaller maps, it's easier to manage events which allows for...
More organic/dynamic world
Having more complex events throughout the game (and not only in main story events) helps make the world feel more dynamic (e.g., PCs respond to more stimuli, NPCs do more than say one sentence for the whole game). Having a large world map with minimal events makes the game feel lifeless. Splitting maps into smaller ones makes it easier to create, keep track of, and QC events which give the game life.
Avoid lag
Supposedly, having a large map (particularly with additional effects, like a parallax background, weather effects, etc.) causes lag. I've seen this when playing some other folks' games. The map is large and "busy," utilizing every plugin the designer could get their hands on, with NPCs all over the place--and there's obvious lag.
Avoid memory leak freezing the game
I'm not exactly sure how it works, but what I've read seems to indicate that if the player sits in one map for too long, the game is more likely to freeze from memory leaks (or a faulty plugin or event). In contrast, when the player goes from one map to another, the memory cache seems to be cleared to some extent and prevents the game from freezing.
As a player...
I prefer maps broken up as a player. It makes exploration feel more manageable and minimizes the feeling of a "walking simulator" (for me, having a screen scroll for a long time creates that walking simulator feeling; I know old school JRPGs did this all the time with their dungeons to simulate a kind of fog of war in exploration, but I'm not a fan).