I use both barley and lentils frequently.

Puy lentils are lovely, but there's a textural element specific to barley that you don't get with any other grain; they are soft but chewy niblets that retain their integrity no matter how long you simmer, whereas lentils cook down into an equally pleasing - but very different - soft mealy texture.

Barley also imparts a rich creamy quality to the broth, a quality that has been used by poor households to stretch the water that meat has been boiled in for centuries and turn it into soup. Megan's oatmeal soup does the same job.

It's always fascinating to witness how necessity becomes gradually established as tradition, and from thence a comforting pleasure in it's own right.