Working on practical projects as a team - good or bad?
Ultimately it comes down to if the work can be done alone? The purpose of group work should not be so that everyone has less work to do, but rather if the original work could not be done within the given span by a single person. In the workforce, you're most likely to be working in a team and contribute to iterative releasts (Agile Methodologies). If your expectation is that because you're in a group, you don't have to work as hard compared to working alone, then you are set to fail.

My suggestion would be to design a project such that bi-weekly or monthly iterations are presented, building up towards the final product. Incorporate Agile Methodologies into this as it is very useful in the workforce and teaches team management / tracking. Groups should be no bigger than 3-4, otherwise it is too big to be efficient. The number of hours required for the project should be big enough that everyone is kept busy. Of course some will do more than others, however one person should not be able to do the entire project.

If this is too heavy for your course, then I'd suggest stick with single person projects as there is no merit to group work.