It all depends the what you needs and limitations are in terms of features, cost, supported programming models, performance, scalability, and reliability.Also have a look at tenant's Regulatory Considerations as a lot of government entities demand isolated storage. You have a lot of tenants so I think a more isolated approach will be better for you in general. Have a look at this
http://msdn.microsoft.com/en-us/library/aa479086.aspx[
^]