You would have to further define specifically which 12 gauge slugs you were refering to, but in general, the recoil is much greater with the 12 gauge than with any .270 or .30-06. I have both an H & R Ultra Slug Hunter in 12 gauge, and a .30-06. I shoot 400 grain Winchester Platinum Tip sabots in the 12 and CT 180 Partition Golds in the 06. Even though these would be considered reasonably stout rounds in an 06, the recoil is insignificant compared to how much the 400 grainers out of the 12 put into your shoulder. Really only mainly matters when your sighting in the rifles though. Never really noticed the recoil from either when your actually aiming at a game animal. The amount of broken blood vessels in your shoulder also helps further show you the difference after you shoot each. That is why I generally recommend shooting a 20 gauge rifled barrel shotgun over the 12 gauge. The 20 still kicks a healthy amount, but your pushing mid 200 grain bullets, instead of upper 300 grain to 400 grain bullets, and I really doubt the deer will notice the difference.