industry standard? Gibson Echoplex Digital Pro. about $1100. For cheaper solutions, it depends on how you envision yourself looping. The right place to research current loopers is at the source: www.loopers-delight.com
I use a Line6 DL-4 and the Echoplex. The Boomerang is a good choice too. If all you want to do is practice rhythms and solos, the Boss or Digitech are will work, but too many functions are only accessable by pressing tiny buttons on the pedal, so you bend down a lot.