All types of earthworms can do the same work, converting organic matter into valuable worm castings, but some breeds do a better job than others, so naturally, we choose the best worms for the job!
The earthworms used in worm farms are in fact compost worms, which are different to the regular earthworms found in garden soil. Compost worms are surface feeders and don’t burrow deep into the soil as garden earthworms do. The various breeds of compost worms, such as Tigers, Reds, and Blues, are capable of eating their own body weight in food each day, so a kilogram of worms will consume that much food daily! By comparison garden earthworms only eat around half their body weight each day, so they aren’t as good at composting lots of material really quickly, as it takes them twice as long. For more information see https://deepgreenpermaculture.com/2014/09/23/worm-farming/