ADA Malaya is a lighter colour and if you want you can put Powersand underneath it, though a lot of people don't use the powersand too. If I had the choice I'd use Aquasoil every time.
Powersand needs to go under another substrate and is designed to supplement the nutrients in Aquasoil. It isn't a sand BTW! It is pumice pieces with peat and other things in amongst it.
If you want a feriliser to go under sand I would go for the Tetraplant Complete. I this is a fine sandy base layer that I found stays under the sand despite replanting plants. I don't think it's in the same league as Aquasoil for growing plants though.
ADA Malaya is a lighter colour and if you want you can put Powersand underneath it, though a lot of people don't use the powersand too. If I had the choice I'd use Aquasoil every time.