Don't currently run an 8, but have played with the Mauser and Rem Mag a little bit in the past. The 180 BT would be a hands down choice for me.
It would be a great varmint bullet in the big eight though. The PD's would probably end up in the next county.
SST's are just a little to soft for my liking in the 270, can't imagine it being much better in the 8.