There are several molecular structures for the amino acid 'L-Arginine'. 

• One advantage of Arginine PyroGlutamate ( APG ) over L-Arginine is that APG's molecular structure allows the  molecule to work in conjunction with L-Lysine.
• A disadvantage of APG is that it costs 500% more than L-Arginine.

L-Lysine should be always used with Arginine Pyroglutamate not L-Arginine