Roman Republic vs Roman Empire

[Mrbsct]

I just saw an interesting poll on which was better, the Empire or Republic in terms of their government policy and their effects on personal freedom, economic power, social mobility, military leadership and military in general/security.

I want to compare:
Mid Republic
Late Republic(Marius-Augustus)

Principate
Crisis period
Tetcharchy
post-Constantine

Which system was "better". The Republic was fairer government system in its intial phases. What was its treatment to city state allies and Socii? Was it better than the Imperial non-citizen system?
I believe the Late Republic was fairly corrupt.

The Empire was more economically secure and provided more proletarian rights. What about its army? The Republican army was very incompetent in their intial phases led by Consuls. What was the military experience of the Republican leaders compared to Imperial ones? Imperial leaders had longer service lengths meaning their campaign can be more thought out. The Republican can levy more Legions due to private wealth of the Senators.

[Timianus]

Not really a fair question, as the Romans considered the republic to be "restored" after Augustus took power and continued to refer to the state as a republic. The notion of a Roman "Empire" is a modern construct. IMHO, it is not really productive to judge ancient cultures by modern standards of what is "better."

More importantly, how do you define "better": 1) more rights to the most people; 2) longest periods of peace; 3) greater ability for social mobility; 4) most religious toleration; 5) wealthiest period; 6) quality of life for the average prol; 7) most stable economy; 6) best able to defend itself?