It depends on which factory ammo you're talking about. If you include boutique makers like Buffalo Bore, Double Tap, Underwood, Grizzly, and Cor-Bon then it's six in one hand or half a dozen in the other. If you restrict the choices to "mainstream" ammo houses like Federal, Hornady, Remington, Speer, and Winchester then .44 Magnum is the clear choice.
Smith, and Wesson, and Me. -H. Callahan
Well waddaya know, one buwwet weft! -E. Fudd
All bad precedents begin as justifiable measures. -J. Caesar