In short, a trademark agent is a non-lawyer with a qualification in the trademark arena whereas an attorney is a lawyer with qualifications in the trademark arena.
But on the whole, the job of a trademark attorney is a very lucrative one, since the field of intellectual property i.e. trademarks, patents, copyrights, geographical indications and industrial designs is a less visited one. Common people generally don’t have much knowledge or interest in this field, especially in India. Thus it is required to have good and experienced attorneys to bail the common people out of the difficulties in this field of Intellectual Property.