I'm leery of the stats on the weapons. I've used both weapons extensively and the 103 is certainly a more powerful weapon. If you're going to focus on an assault rifle, grab all the passive skills, and every rifle as well. You'll find yourself downgrading to the Tier 2 rifle for some builds, and really won't want to use the AG-74U.
Finally, definitely get the grenade launcher and it's reload speed. It's an excellent tool, especially for finishing enemies and clearing rooms.
MAG Divisional Lead Officer - S!K NAT!ON