Having shot both I can say that the two grips are very similar and I had no issues transitioning between them. The Magnum grip may look bigger in photos but doesn't feel bigger in the hand. That being said, Gregg will work with you to get you the grip you're looking for. He really is a master of his craft.
You just can't go wrong with an Elkheart, whether a standard or Magnum. I ultimately chose the Magnum because I wanted the shortest Elkheart I could get for my draw length.
I would encourage you to talk to Gregg about what you're looking for in a bow, he will steer you right. And even though I'm shooting a Magnum at this point, I would gladly have another standard Elkheart.