What are the pros and cons of leaving the different ports out of Italy to Greece? I have always known only of?

Brindisi, but now I hear there is also Ancona, a port out of Venice, etc. Anyone have any information about the pluses and minuses of the different choices? Length of time, cost, convenience, etc.
And what port is best to enter in Greece?

No difference between ports of Italy. It depends on where you are when you live Italy for Greece.
The departures are from Venice, Trieste,Brindisi, Bari and Ancona, .
The duration of the travel depends of the departure/destination and the speed of the ships.
To Patras (Peloponissos) the shortest duration of travel is from Brindisi or Bari (approx. 15-17 hours)
To Igoumenitsa (Ipiros) is from Brindisi鈥?(approx. 7-9 hours)
On the ships it is possible to reserve cabins of all the categories with services or without (so the cost depends of you).
The departures are mostly in late evening with arrival the following day.
The port in Greece depends of your final destination

you can find every information you need:
http://www.gnto.gr/?langID=2

Well,of course it depends on where you are in Italy.If you are in the southern side,as you said,Brindisi is one of them.In the northern side there is venice harbor.If you are in the north-west side of Italy,then Genoa is one of the biggest harbors.In Greece,mi aunt set out for Greece just today and she left from Ancona harbor towards Patrasso harbor which I guess is Athen's biggest harbor.
Hope it can help you.

Ancona is less congested