Potential advantages of combining shells:

• Saving time and effort -- the creation and maintenance of one course website versus separate courses for each section; all of your improvements and modifications are consolidated in one shell; 
• Greater accuracy -- doing things only once reduces the chance of making errors;
• Consistency of content for all sections --  be confident that all of your students are getting the same information;
• Leaverage your creative efforts -- create special documents, study guides, or layouts that benefit allof your students;
• Increase diversity: of people, of opinion -- you have the option to involve all of your course sections in common discussions and group work;
• Emailing all of your students or an individual student is easy

Potential challenges of combining shells:

• The gradebook includes students from all the shells that were combined;
• Manually entering student grades can be more time consuming as it can take longer for this large gradebook to load and reload after each grade submission; it's recommended that you use Gradebook Views--by User or by Item--to manually enter grades.
• To avoid manual grade entry, use the View/Complete assignment tool (students submit their assignments directly to the gradebook);
• Separating students according to section requires planning and some effort.  However, placing each section in a different group makes it possible to:
  • Keep discussions separate between sections
  • Email students by section