A ‘mala’ is a case made out of plastic, leather, canvas, vinyl or some other sturdy material, with a hinged lid and a handle to make it suitable for carrying clothes and other luggage. So a suitcase or trunk.
It can also be a woman's handbag, more or less synonymous with ‘bolsa’, or the boot of a car, or slang for someone's stomach or abdomen.
In Brazil it can informally also mean a bore (in the sense of a boring person) or it can be a vulgar word for anus or penis.
A ‘maleta’ is a small suitcase, typically one of those on little wheels with an elongated handle that you drag along behind you.
Here's an example: http://milvuelosbaratos.com/wp-content/maleta.jpg
But it can also be used for a variety of other kinds of small suitcases.