Open-world maps that you travel through to reach one location to another (as eschaton said) is definitely for those with attention to detail and kind of "bringing the adventure immersion to focus". The player gets the feeling of real travel, making their way from the town at the bottom of a mountain to the very top every step of the way, instead of just warping there in 10 seconds. These types of maps can of course be challenging to make because you have to avoid repetition while keeping the player interested in the scenery as they walk/run through for various maps before reaching a new location. Usually this mapping goes well with games that allow special player abilities to either allow getting through the map, blocking players from taking certain paths, or just as puzzle obstacles. (in terms of Pokemon, cut, strength, rock smash, surf, etc.)
Over-world maps (most old JRPGs) are for games that want to specifically focus more on the locations themselves rather than how the player gets there. These games also tend to focus more resources on other game-aspects since they're not spending much time on maps, like battles, location designs, story line, cut-scenes, etc. However this is only limited to time and budget, and if you have plenty of those as a casual RPGMaker user then you don't really have to gimp yourself as you have all the time in the world.
Both are very valid styles even to this day, but if I had to prefer one for myself, it would be open-world maps. My favorite title of this type was Sword of Mana for the GBA. Also a good RPGMaker game that uses this style is
Lunar Wish: Orbs of Fate if you want to check it out for ideas.