There is a time and place for both individual projects and group projects. The decision here often lies with the type of project/content, the learning level of students, and the learning preferences of students. I have had projects where I allow students to choose if they work in pairs or individually. Some students really prefer one method over the other. We tend to assume that students always wish to work in groups but believe it or not there are always students who want to work alone. This is really an area where you have to make the decision based on your knowledge of the content and your students. Sometimes, working with a partner will help the students have constructive conversations and learn more. Other times, one partner will do more and learn more so group work isn't best.
I suggest, when determining between individual verses group projects, you consider two major points.
First, consider limiting the group size. Personally, I prefer groups of 2 and on occasion if needed 3. In groups that are too large, often someone ends up not doing much to contribute. In a group of 3, 2 students may do the majority of the work while the 3rd student observes (this is especially true in a lab setting). Having said all of this, there is one lab at the end of the year where I have larger groups of 4 maybe even 5 students, but in this lab, many hands are required. Each group must assign jobs or the lab cannot be completed well or in a timely manner.
The second major point of consideration is - be aware that when students work in partnerships/groups they tend to divide up the work. Great - yes we expect this. However, at times this can have the same type of result as the jig-saw method. For example, two students do a project together over ionization energy and electron affinity, and they divide up the work. One student may become an expert on ionization energy, and the other student may become an expert on electron affinity. On a future test, each student may only pass the questions over the portion they learned. All of this to say...be aware of this potential pitfall. Projects are good in the appropriate time and place, but we as teachers have to consider the topic and desired learning outcome - then plan a project with parameters that will help ensure the desired learning outcome. Many teachers approach this problem by telling their students they are responsible for all the information. I put forth to you the idea that if telling our students this doesn't work, we should consider getting rid of the group work. Meaning that while we say students are responsible for all information, if we observe that they do not take ownership of all the information, then we as teachers should correct the problem by turning the group project into an individual project.
Happy Teaching :)
-Founder of Chemistry with Confidence