How does a Muslim differentiate between fatwas issued by trustworthy scholars, and is it permissible for him to adopt the easiest fatwa?

It is not permissible for you to choose the easiest fatwa; rather, you must fear Allah and follow the truth. The choice of a mufti is based on two things: his piety and righteousness, and his knowledge. If these two qualities are combined in a mufti, the soul is reassured by his fatwa. If two muftis are equal in knowledge and piety, then preference is given to the one who mentions the arguments of the other and refutes them. A mufti is like a doctor, so choose someone who is keen to clarify the truth for your religion, even if it is difficult for you.