[Widsets] is a Java platform, so it’s not open. Widget Manager is built on Opera, so it’s faster and easier to write for. It uses open standards.
Easier to write, shorter time to market. This basically echoes Opera's position. Using open standards makes it faster and easier to develop applications. Opera is pushing for widgets based on open standard, and Vodafone seems to agree that this is a good thing.
So now both Vodafone and T-Mobile are going for Opera's widget solution rather than competing technologies that are proprietary and more difficult and time-consuming to work with.