it just depends on what sound you are after :?...
This is the very point of BKP, and the hardest part. As i did, i went for the ones Tim recommended me. Not only does he produce them, but he has a basic understanding for what genre the pickups where made for. Whatever BKP you choose, you will be more than pleased. Just a tad more particular.
Anyways, your asking us, right? So heres the deal:
The Nailbomb contains a great old school thrash tone, like Megadeth and Testament. A more open tone compared to the Miracle Man, thats at least my point of view.
The Miracle Man on the other hand, is one of the "modern" pickups BKP has to offer. Think metallica: Hi-Gain ceramics. The more modern bands as well, but the newer bands contain too many other genres to be classified as pure thrash.
Conclusion: I love the Miracle Man, because now im more into the heavy, tight and POWERFULL guitar tone. But i still use the Nailbomb when i need the classic thrash feel that i have fallen in love with.
Miracle Man is my personal favorite, but for you... NAILBOMB. Just listen to the freaking name!