Board Thread:Dark Souls II/@comment-25071275-20150426020545/@comment-4511886-20150623173944

I believe you still get as much Souls as before, but as a summon you get less Souls (50% less, if I'm not mistaken).

As for the damage reduction staying, I think it's mainly because the extra defence is added on spawn, so the boost is there until the enemies are respawned. Then again, it also has some value for balancing, as the Host wouldn't have as much pressure to keep their summon alive if the defence was reduced, as there would be no negative consequence compared to not summoning at all.