Within the last decade I have found the quality of remanufactured parts has gone down to a 5 year life spann; Most especially at the national chain store auto parts. A local guy still may give you good reliable service with a longer life span on alternators or starters.
On our cars I will generally go with the OEM part as they are of the highest quality. Our starters and alternators are 12 years old now and few have been replaced. ZERACER said the time and labor put into changing out the problem part is important to consider, and I do most all the work on my cars it is often the most important consideration when looking at $100 difference in price.