Colin Scott who used to post regularly stayed in Algerho and was not very complementary about last winter over there.
He seems to out of regular touch for posting at the moment but if you do a search for ccscott49 you may find his posts.
THe new marina Porto Turistico di Roma is really fantastic. We wintered there (living aboard for a spell, then returning back & forward on cheap flights to London) last year. There is large group of cruisers who live aboard - mainly called "Med Net". They were really organised, had VHF meetings in the mornings, Sunday get togethers and all the cruisers contributed to our own 'Yellow Pages' as everybody found various bits (anything from video libraries to anti fouling). The marina has an excellent chandlery, bars, restaurants, shops, 24 hour CCTV security, washing machines, excellent shower blocks, friendly staff (who speak english) and topped off by being located 15min from Fiumincino Airport. Rome centre is also easy to get to (and only 55c).
We liked it so much that we bought a berth there. Our boat is now in Malta and we're heading to the Adriatic, so it's available for long or short term and I would like to rent it so I'm offering it cheaper than the Port. It comes with a a car parking space if you'd like to rent or buy a cheap car for your stay. Please email me if you are interested: greg@jacksonsbayretreat.co.nz
I've wintered in both although I'm not a full time livaboard. Alghero is a beautiful city and there are some great places to cruise out for the day...however there is a strong swell in the harbour which breaks springs and is quite uncomfortable at times. The marina staff are excellent and really look after the boats though see: http://www.ser-mar.it/sitouk/indexuk.htm
I'm in Porto di Roma now and soon to got to Barcelona but a very safe location with very little swell especially on the D pontoon, Huge livaboard community of 30 odd boats with something organised most nights.
Only a euro to bus/train into Rome but the coastline is hellishly boring with interesting bits 50 miles North and South
hope this helps