Glad you posted this thread. I've had the same questions, having spent no time actually backpack hunting. I have an Eberlestock X-1 for day hunts, capable of packing out a whole whitetail, though fully loaded. However, not enough room in that to pack in a spike camp for several days.
I have a Kelty Coyote for packing in, but it's a little big for a daypack though can be cinched down fairly compact.
Couldn't see carrying an extra pack just for day hunting and I am certainly in the camp of "packing the first load back to camp" and needing enough pack to do that.
Using my main pack for a daypack makes more sense to me.
