The main disadvantage would be that defenses are played by black. It's just chess terminology.
If you mean mirroring those same opening moves, except on the white side of the board, then the disadvantage would be that those are world class defenses for black precisely because they react to specific, good opening moves white frequently plays. When those same moves aren't made in reaction to opening moves, but on their own, they tend to be a little bit passive.
Both sequences are, however, still playable as white if you have the inclination (and if black doesn't force you to play something else along the way).
I'm fairly new to chess, and especially to Chess.com, but I have enjoyed learning, playing, and meeting fascinating people from all over the world.
On the Indian defences, the examples that I've seen usually show them being played by black. What would be some advantages or disatvantages by playing them by white?