All are good choices. Since you already have a full size pistol it is hard for me not to vote Glock 19. But I would say go for the model that fits you best.
I would base your purchase on the use of the firearm. For a carry I would go with a g19 for range/training choose a fullsize. Since you already have a full size Sig I would lean towards a good conceal carry. Xdm 3.8, g19, m&p shield