The business-oriented newspaper, El Financiero, just published an article talking about the advantages of performing a migration instead of a manual rewrite. The article talks about how Banamex (part of Citigroup) saved an estimated 80% of the cost when compared to rewriting their 125 applications, totaling over 5 million lines of code. It also talks about the advantages of being in .NET, including how it allows customers to rapidly respond to changes in market conditions.
You can read the original article in Spanish at the following link: Cambiar el software en estos tiempos de crisis or read the Google Translation in English. You can also check out the Banamex/Citigroup case study at the following link: Banamex - Citigroup turns to ArtinSoft to ensure compliance and business continuity through massive migration to C#.NET