Should I UV map a joined mesh or keep the meshes separate when exporting a character to a game engine? I want to create a character with a weapon and then export it to a game engine.

Should I join all the meshes (character and weapon) and start UV mapping so I have 1 mesh and 1 texture or do I need to UV map separate meshes?

What's the difference between the two ways?

I want to create a character that only has 1 unique weapon, like in League of Legends.
As the weapon its other independent object I would not join it with the character, and you can use as many texture as you want if you have different materials.