Subject: is it better to use a dry ice bath or liquid n2 for freeze drying?

i know that the temperature of liquid n2 is lower than dry ice in an 
ethanol bath, but i have also been told that since the liquid nitrogen 
boils so vigorously that an object would freeze faster in a dry ice/ethanol 
bath (heat transfer would be more favorable if the object were not 
surrounded by a gaseous phase).  i cannot find any information on the 
validity of this claim.  can you help me out?

Re: is it better to use a dry ice bath or liquid n2 for freeze drying?