The type of drug delivery system that is required now is the one that
(1) is non toxic and biocompatible, (2) is stable in biological media- ie. resistant to disintegration, agglomeration or degradation, (3) shows minimal interaction with the blood components- cells (activation or cytotoxicity) and proteins (binding), (4) results in minimal clearance by reticuloendothelial system, (5) causes minimal immunological reactions eg. CARPA, (6) posses 'targetability'- ie. deliver the payload to the intended target, (7) is able to cross natural barriers such as BBB, (8) is able to release the drug at desired concentration over an optimum length of time and (8) smart (eg. pH controlled, temperature controlled....).
It doesn't matter which material you choose, as long as you can fulfil the above pre-requisites, you will be on to a winner. Good luck.