Roblox is the better one, Roblox provides many different ways for creators to learn easily and quickly on how to build their own custom games! They can use free models or learn how to script to make the most ultimate game they can think of! Minecraft as well provides a way to do this but you sometimes can't expand as much as you can in Roblox. In Roblox, you don't have to learn how to script or code or use free models, you can just play the game like it's part of your daily routine. It also provides a way for you to constantly have updates on your favorite games and be able to talk with other people online while playing one of your favorite games together! Minecraft's community is 50 50, some players are nice and some aren't the problem I have with it is that when I'm trying to scroll through youtube shorts or something, I have to constantly deal with stupid people that try to make you subscribe or like their videos for something "special" although Roblox users have caught onto this, it's really dumb to spam something like this.
Literally, if you go on one of these spam accounts, most likely literally the ONLY thing they upload is the EXACT same VIDEO. But that's just Youtube, the main problem I have with Minecraft is that you can't expand your creativity as much as you want like in Roblox where you can either insert free models or make them yourself. Here's what I'm trying to say really, I'm saying that Roblox is better for building and possibly when you feel like playing with friends and other things unlike Minecraft.