Okay so basically when to use movieclips for memory usage:
– If you have repeating motion, ie. Character walking
– If the objects don’t have any changes across multiple frames, ie. Backgrounds consisting of bunch of stickfigure/sprite props.
– You can recycle a part of the animation, ie. effects such as manually created explosions.

You can also go a step further in some cases and utilise delay frame to cut down on some factors. Since the app won’t have to remember the properties of the movieclips then, such as position, scale etc.

If you’re putting just straight up one-off character animations, it would actually lead to slightly bigger memory usage. Although it’s not too bad, if it would help you organise/compose your project better.