Out of curiosity, why do the Orthodox say that Mary should be on the left - what is the reasoning?
The tradition of having the Theotokos at the right hand of Christ - on the left of the icon of Christ (as you are looking at them) comes from Psalm 45 (46).
1) My heart overflows with a noble theme; let me recite my verses for you, O king! My tongue is as nimble as the pen of a skillful writer.
2) You are the most handsome of men, and graciousness flows from your lips; the blessings God has given you can never fail. 3) With your sword at your side, mighty warrior, gird yourself in splendor and majesty; may glory make your conquest complete! 4) Ride on triumphantly in the cause of truth and meekness and right. 5) Let the deeds of your right hand win you renown, for your arrows are sharp, and nations shall fall at your feet in terror. 6) The eternal and everlasting God has enthroned you; your scepter is one that rules true; virtue you love as much as you hate wickedness. 7) Rightly has God, your God, chosen to anoint you with the oil of gladness, setting you above all your companions. 8.) All your robes are fragrant with myrrh, sandalwood, and cinnamon; from ivory palaces the music of strings entertains you. 9) Royal princesses take their place among your honored women; at your right stands the queen
, dressed in a robe of many colors, embroidered in gold.
10) Listen, daughter, and see! Give ear to my words: Forget your people and your father's house. 11) The king is enthralled with your beauty; honor him, then, as your lord. 12) O daughter of Tyre, the wealthiest people will court your favor with gifts. 13) All her robes are royal apparel fringed with thread of spun gold. 14) Arrayed in richly colored brocades, the maiden-bride is led to the king. 15) Those in her train, her companions, are presented with her; with joy and gladness they are brought in; they enter the palace of the king.
16) As for you, O king, your sons shall be worthy of your fathers; among them you shall divide the world, giving each his domain. 17) And may this song make your name remembered from one generation to the next, that nations may praise you for ever and ever.