Efficiency

I primarily mine, and when the new weapons info update came out with the efficiency category, I more or less didn't pay too much attention. Now that I'm looking at new weapons though, what exactly does it mean if really known at all. Is it related to dmg/pec? When I look on entropedia, I get the inclination it's related assuming except that it doesn't factor in your skills (e.g., efficiency is if you had max skills for that weapon)?

Am I better off just picking a weapon based the old way on dmg/sec and dmg/pec instead of the efficiency rating, or is the efficiency metric something good to choose weapons by instead?

efficiency between 0-100 affects tt loot returns by up to 0-7%. dpp now affects loot composition (if i am recalling all of the posts correctly). soo.... more efficiency = more tt return, more dpp = more stuff in loot, less shrap.