I like both games but in my opinion roblox is better.
1. The commuity
roblox has a friendly community.
If there is a player being mean to you you could get him reported.
In minecraft there isn't really anything you can do about a mean player unless the server you are using has a ban system coded into it.
2. Advanced building mechanics
Minecraft has great building but compared to roblox, roblox is better
as it is more advanced, minecraft is simple, place blocks to build stuff. Roblox however has roblox studio, where you make incredible 3D worlds with a large set of advanced tools such as scripting tools and modelling tools which will help you make advanced stuff such as planes,cars,tanks and much more.
I'm not the type of person who prefers graphics over game-play,
but in some ways graphics can be quite important too.
Minecraft's graphics are absolutely terrible compared to almost any game.
Roblox has graphics that aren't very bad or very good, which in this case is better than minecraft.
minecraft is fun to play for a few days but you will get bored quite fast without mods.
Roblox has thousands maybe even millions of games people have made to play so you will probably get alot more playability from roblox than minecraft.
obviously roblox is better for price as it is a free game, (unless you buy bc tbc or obc.)
The community in Roblox is just plain stupid. In Minecraft, once you buy it you get everything but in Roblox, its basically a pay to play game. Just because Roblox is free doesn't mean its completely free. Honestly Minecraft is better because of all the content. There is single-player unlike Roblox.
To be honest, I play ROBLOX and Minecraft, but if you are telling me to decide which one is more better, it is Minecraft. Minecraft have mods, resources packs, skins and imagination full of creativity without any limit on how many blocks, heck you can have a infinite blocks! On the other hand, ROBLOX have a maximum block limit which lowers down the creator's imagination and their catalog is kinda running out of ideas. Minecraft do not need any safe chat system to block out words that not even bad words or inappropriate words like FNAF (Five Night At Freddy) or people's username. It clearly makes no sense for ROBLOX to block words that not even bad and responded with this; ######. Minecraft don't block out all the words, but probably only a few if necessarily.