The quirks of Royal Mail...

Pondering.  In the last three days I have sent out ten parcels.  By the law of averages they won't all arrive on time, but what of the three I sent out Monday morning?  The two second class parcels arrived today, whereas first class Hector is still in transit!!!  Languishing in a depot somewhere, awaiting delivery. 
And I am left wondering.  In 2012, is there really any difference between first and second class post, aside from cost?