I like both to be honest. (Oh gosh, I’m really going to expose myself here XD)
You see, Roblox varies in what kind of games it has and tends to be more “minigame” style or constant-come-back-to games. For example, Work At A Pizza Place is a gently paced teamwork game that you can come back to as you build up your house with the money you earn. The visuals for MurderMystery are, in my opinion, better than Minecraft’s (I mean, c’mon, you hear the knife when the murderer holds it, you see the funny- okay, not really funny- expressions of the corpses and you get to update and trade your weapons!). The tycoons are also really addictive. And I just have to mention Flood Escape - it is my favourite Roblox game and it would lag too much on Minecraft.
Minecraft, on the other hand, focuses on more combat games that involve more strategy. For example, Survival Games is a beautiful favourite and there aren’t any chests in Roblox so I don’t know how they would pull off this game. Also, The Best Builder is something Roblox can’t do as well as Bedwars, Skywars, One In The Chamber, etc. Do you know why? Because Minecraft has the advantage of creating, destroying (mining) and all its different blocks which Roblox doesn’t have.