The pros and cons varied, depending on the time. Roman history, from the founding of the city to the fall of Constantinople spans around 3100 years. Naturally, circumstances were always in some degree of flux.
In all of the thousands of years of recorded history, there are fewer than 300 years of recorded peace. For the Mediterranean world, 207 of those years, from 27 BC to 180 AD, from reign of Emperor Augustus to the death of Emperor Marcus Aurelius was called the Pax Romana, or the Roman Peace. No where and at no time has any other human institution been so successful for so long.