What qualifies to be an "all purpose flour"?
Of those two, Maida flour is the closest to 'Western' all-purpose flour (which is an American term. It is called plain flour in Britain). Atta flour is made from durum wheat, which is used for things like pasta (and of course Indian breads like chapatis). 

Maida flour is made with 'regular' wheat, but it also has a lower protein content than all-purpose flour (8-10% as opposed to 9-12%). The impact of this lower protein level will depend on what you're cooking. Maida flour should be good for making cakes, for example.