Choosing between clone based or differencing disk based VDI for a Deployment

Good day to you! When it comes to working up a proposal for a customer, I'm always in a dilemma of whether to propose a clone based or differencing disk based VDI for a deployment. What's the pro's and con's in this? The obvious one that I can see is storage space savings. How about the performance in terms of log on and log off speed. What other issues are bound to these implementations? Correct me if I'm wrong, since differencing disk based implementation can also has the look and feel (with vWorkspace User Profile management) of a clone based, should we always be using differencing disk method? Thoughts anyone?

Regards,

Cyril