The perks offered for the Arminius aren't great. Hold onto it until it has counterbalance and braced frame. Hold onto the Dis-47 until it rolls with full auto and hand-laid stock. As 2 of the best weapons in the game right now (for PvP), I'd hold onto these packages each week until you get those perfect rolls. Edit: It seems that many people don't know that if you hold on to the package, it will re-roll each week with different perks. If you like a gun but not the perks on offer, keep it until it has the perks you want.