The increasing complexity of the teaching profession calls for engaged professionals in their professional development. This article claims that participative types of research contribute differently to professional development. Its intent is to explore the different contributions action research and collaborative research bring. One action research and one collaborative research have been conducted involving school personnel. They have been assessed mid-course with regard to various components of professional development, including the learning taking place, changes made to professional practices and development of the collective competencies. Group interviews were conducted and each participant produced a written summary. The results show that participants' individual competencies are strengthened, as well as collective competencies emerging such as the development of a common vocabulary and a shared vision about the school's mission and mathematics curriculum. Learning is more relational in the action research project, and more connected to knowledge in the collaborative research project. Tensions are also present. They deal with the need to come up with concrete results, the urgency of action, the need to be open to the unknown, a tacit agreement to expose one's vulnerability to others, the need for interdependence and for accountability. In conclusion, researchers identify their own sources of tensions and recognize that those types of research are important situations of learning.