It depends on the game you want to make. Plan the features of your game beforehand, proceed with a rough idea of what you want to do. Do some research on scripts and plugins used to achieve those features and see if they're available for the engine you want to use. Also think about assets. like, would you rather use the size of MV characters or Ace characters. And see which engine has more/better resources for your game. And last, see which one you're more comfortable using. It might take some time to get used to a new engine.
Ivockrenim, I don't think an answer can be given without more information honestly...because the answer should reflect what you personally want to do for your game project and which engine would be better suited for it. Both are great engines, and I would like to mention MZ is being released as well and something you might want to consider (if you were not aware). What are you going to do yourself and what assets are you going to utilize from other creators, and are those assets ready for one version or the other, do you have the skills to alter those assets if they are not questions like that. What things are most important to you in a game engine? Are you going to use the built in assets and if so, which do you like better? I personally am building my project on MV...
Really depends what ideas or plans you have. They're basically just the same but uses different grid sizes format, tho you can port it to android and other devices in MV(IDK if you can also port games in older versions).
MV has better fullscreen, flexible resolution optoins, multiple port options, more modern resources, and is more modern so it has better support.
If you have no idea what you're doing (you don't know much about RM, can't write your own plugin): MV (or wait for MZ). The previous RM support is kinda dying. You won't see a new script written for them, at least not very often. The resource being made and all.
If you know what you're doing: Pick whatever you're comfortable with.
Excited to be nearing the end of setting up my own custom Point-And-Click system template! Just need to iron out some kinks, get an input text system going, add animations to buttons, and then finalize my button-mashing event system and it'll be complete >:3c