In attirail, there is the idea that it is a lot of stuff, and that it is not so practical. It is mostly ironic. Matériel is more factual.

Un attirail is usually really cumbersome. Most of the French will actually use it in a pejorative way.

When you show up with a ton of unecessary stuff, you will be welcomed with a :

Mais qu’est ce que c’est que tout cet attirail !