mRNA capping kits

[Alan Hair]

I have just done a direct comparison between Ambion's mMessage mMachine and
Stratagene's mCap mRNA capping kit.
 While both kits gave full length message the yield of the MM kit was at
least 10-fold higher. 
Anyone any suggestions as to why?
Does MM kit have some 'magic' ingredient? 
Does anyone know how these kits compare in their relative capping
efficiencies?
Thanks 
Alan