They are two different airlines with two sets of rules - sometimes you win with one, sometimes you win with the other.

I have no idea about the BA scheme; as I always thought MFU meant Miles For Upgrade, but the Virgin Miles Plus Money scheme is rarely an attractive option in my view. It is not pitched at the frequent flier, but at someone who travels occasionally as it offers a way of using points to save a few quid. (usually)

M+M tickets do not earn points, and there are sometimes cheaper points earning fares to be had - especially during sales.

If the BA options suits you best - go for it!

Nick