This is an excellent framing that's rarely expressed. Most people focus on the tax aspects, and that makes sense - it's easy to feel a sense of injustice if you think others are somehow getting away with paying less tax.

In reality, the actual difference is marginal, and in return contractors forfeit every protection taken for granted by permanent employees. Paid leave, sick pay, redundancy pay, protection from indiscriminate firing, (often generous) pension contributions etc.