As self loading freight I have always been reassured by the presence of Halon extinguishers in the aircraft cabin. I have seen many demonstrations of fire extinguishers and given quite a few myself. Halon has always come out on top for ease of use and speed of knock down. For an aircraft cabin fire there is nothing to better a hand held Halon extinguisher.
There is a considerable difference in characteristics between fixed fire fighting systems and hand held extinguishers. For engine fires where there is fixed 'plumbing' there may be a suitable replacement...BUT please remember the papers posted previously on this site are by the manufacturers of the replacement extinguishing agents! Note also that some agents use Nitrogen as a propellant gas, OK, we breath it all the time at 78% concentration but it will suffocate at around 91%, not good for use in a cabin?
As far as dry powder extinguishers go, if you have not seen one discharged, or discharged one yourself then you are in for a treat! Visibility goes immediately and the white fog that ensues takes ages to settle as a fine white dust. This would be guaranteed to cause panic if used in the confines of an aircraft cabin.
IF, as mentioned in a previous post, extinguishing powder can damage metal (and presumably aircraft alloys are more reactive than most others) then one discharge could be a very serious problem to the airframe as the powder gets EVERYWHERE.
As far as 'Pinkman is concerned' - he can walk out of T5, I don't fancy walking out of an aircraft at 35,000ft when the 'EU suitable replacement' fails to check a small fire which halon would easily cope with.