Plain an simple. All Armatrix weapons are more economical and get bonus loot for higher efficiency than pretty much every other weapon in the game up to at least 56% efficiency. I spent a few hours playing with numbers yesterday, and until you start getting into special event weapons like the mayhem weapons where efficiency is now arbitrary instead of an indicator of the economical value a weapon has, the armatrix outclass pretty much all other weapons DPP wise up to at least 120% mark-up across the board, and even up to 130% in certain cases. Now this is dependant on using the most efficient amps available. Don't bother buying unlimited weapons, unless you need something with tiers for more damage like for events, but for normal grinding and skill training Armatrix is the way to go almost every time. For higher mark-up costs it will vary on a case to case basis, as some weapons did beat out Armatrix with proper amps. As a weapon approaches 60% Efficiency the numbers get mirky and its best to do the math but throw on a p20 extender you paid 105% for, and now the math gets that much more fun vs an unlimited gun.