I choose the doggies. I tend to solo a lot, and that means a fair amount of time I have the zombie out with defensive stance. In those situations, I benefit much more from having upgraded doggies.
For grouping, it's hard to say. I would want to see a detailed parse of the adept3 dogggies vs the master 2 doggies. To see if the 8 or 9 percent haste difference is worth it.
But I've also kept in mind that I have at least one respec left to use. So I know that if the situation changes when Im level 60, I will be able to change my master 2 choice (though since I will get adept 3 offense stance, it will be sort of a waste to switch)