There are several ways to measure the success of IT projects. projects meet objectives within time and budget, delivered features, and the quality of the delivered product. There are other indicators such as productivity of developers and number of detected bugs. More information can be found in this paper where the focus is qualitative analysis.
There is software development inside IT project. Therefore, success of IT project also depends on success of software development. I would suggest that you focus on software development with agile practice rather than seeing it from IT project perspective.
What do you mean when you say Agile Project Management? To some this is a contradiction in terms to others it is innate to proper 'regular' project management. Yet others understand it to be the application of the DSDM Agile Project Framework. Also what do you understand the success of an IT project? It's ability to deliver on time/on budget or the degree to which the underlying business issues have been tackled?
The key is not whether Agile methods are used, but rather in defining the measures of success. Agile approaches can be used in all phases of a project from requirements elicitation through incremental deployment. There are success metrics that are independent of the project management approach used, so if you pick one of those then measuring success is problematic. The experience of the people and the nature of the solution are also factors which can make measuring success difficult. Is success minimizing cost, minimizing delivery time, maximizing requirements fulfilled, building a sound basis for a product line, building a revolutionary or innovative solution, and/or creating a profitable product? Any or all or part or other success factors could be valid, but in order to measure success you have to be accurate and precise about what you measure and why.
I come from a traditional waterfall project management background. 15 years ago, I got involved in agile project management. To measure the role of agile in the success of any project is contingent not only on the successful deliveries of multiple streams, rather on the success of the overall delivery of the solution. I always present an analogy to the team working with me, it's like having to load different cars to a train. It is not enough to add one car to the next, rather you need to make sure that these cars will be easily dropped off (one after the other) at different stops/destinations.
Podrías medir los resultados obtenidos almenos en alcance, costo y tiempo, en un proyecto con y sin metodología agil. Luego evalúas que lecciones aprendidas te deja cada uno.