AR70 is functionally a three-star counterpart to FAMAS or XM8 - significantly better in terms of damage and evasion, but worse in every other stat. What this boils down to is that AR70 is amusingly average in role, having no really glaring advantages, but no real downsides to speak of. What she offers over her four-star French cousin is Antipersonnel Grenade, which makes her good at damage spiking and much more utilitarian. Over XM8 she offers better damage and HP.
All in all, while not a fantastic rifle, AR70 is a decent choice, if somewhat of a rarity, especially for a Commander on a core budget.