RDM416 makes some good points and presents a good comparison.
My experience is on a 338 RUM 300gr Hybrids, 10 lb rifle Holland QD brake. No such thing a even close to pain. Shoot all afternoon prone in a tee shirt. Spot all shots from 100 on out.
270 Allen Mag, DE Brake. 12# rifle, recoil is way less than the 338 and can spot all shots from 100 on out.
375 Allen Mag, APS brake, 17# rifle. Recoil is similar to the 270 AM. I was very surprised at the first shot. Spotted the shot @ 1k. Shot two more to validate the surprise of the first.
You'll hear the 7mm AM shooters with 16# guns say it just twitches with the DE brake. The 375 does just a bit more than that with the big APS Painkiller.
A serendipitous feature of the big PainKiller is that it's perfect for holding the iPod to get an accurate shot angle. Remember to remove it before ya brake the trigger.