Panels vs Block

Hi Guys,

I've read somewhere (can't find it now :( ) that it is better to use panels not blocks . I can't remember weather it was about curtain case or in general.
Can anyone please recommend me a good article where I can read about differences between panels and blocks and advantages and disadvantages of use both?

Regards
Evo

_{Edited by WorldFallz - moved to appropriate forum.}