Fade behavior VS Fade animation ??

I wonder..

So i have a lots of enemy sprites that i want to decrease visibility if a player collides with them and..

Which choice is better if i run my game in mobile devices?

1.) adding fade behavior to it?

2.) or create a fade animation.(like a series of sprites that decrease opacity over time)

They are both doing the same thing, decreasing opacity of an object.

Fade behavior must be better. With lots of frames in animation your images are using more memory.

Oh by 2 I thought you meant create your own fade animation using opacity. Don't use an animation.

alright, ill see to it, thanks for the response guys :-)