What are the differences between D and L glucopyranose?
They are mirror images of one another and therefore their chemical and physical properties are the same, except for the deflection of polarized light, which will be in opposite directions. 

Mirror image compounds that are not the same are called enantiomers and it does not matter if they are in the open or cyclic form. 
They will, however, have different properties if they are in a chiral medium. 
For instance, if placed in a chiral solvent, they will have different solubilities. 
Chiral means that the compound has a mirror image that can not be superimposed on the original structure.