Key issue is how you weight the attributes. The Gartner Group has suggested different weights depending on the nature of the application environment:

  Stable
Environment
Dynamic
Environment
Technology 0 15%
Functionality 40% 15%
Cost 50% 10%
Service/Support 10% 15%
Vision 0 20%
Ability to Execute 0 25%

Based on material from the Gartner Group.