VFC M4's all have 8mm metal bearings so there lipo ready off the box.

Any gun is "Lipo ready" per-say, just a question how long it will last and what type of Lipo is used.

As much as I don't like them, I'd say an M4 over a Scar any day.
There is a huge chunk of options/parts you can do with an M4 any day any time.