I think both pickups will perform well, the only difference being that the Painkiller in deed has a higher mid peak compared to the Aftermaths center mids. They are both tight, clear and can give you a Meshuggah-like sound without a problem. I've chosen the Painkiller over the Aftermath since I found the trademark "quack" it seemed to have in every video a bit annoying.
No experiences with the Nailbomb, but it should perform well in the Loomis in deed.
When in doubt, just e-mail the BKP team. They know their products the best :)
Good luck and cheers