When taken alone is does not matter very much which form you take. But when taken in combination with other amino acids (for example in a proteine shake), glutamine peptides are superior.
A study concluded that if L-glutamine (a free amino acid) is consumed at the same time as other proteins or amino acids, the L-glutamine has no effect on muscle growth. A peptide bonded amino acid, such as peptide bonded glutamine, has been shown to be absorbed up to 20 times more effeciently than a free amino acid, such as L-glutamine, in the prescence of other proteins or amino acids because peptide bound amino acids are absorbed via a less competitive absorption mechanism.