The factor would be the ultimate entity (structural motif) and/or functional efficiency responsible for carrying out the work you intend to do which would need to be generated from these two, seemingly equivalent, ligands of Arginine. If they produce one unit (structural motif or the equi-scale measured functional measurement producing the same amount of work) per mole, they will be equimolar and you could use them accordingly for single mol of either ligand, otherwise use them differently which in any case, eventually, you need to calculate or measure out for getting the equivalent work as per your available ligand. This could be done on calculative basis together with literature sourced information!