I did a LOT of pellet testing in a bunch of game mediums 12 or so years ago with every pellet available in .22 and .25 at the time. From Bear/deer/hog down to sparrows. That being said, I've now done some real world testing with some of the new slugs and can offer some advice. Now, understand that without question accuracy and knowing the anatomy of your animal, ie. shot placement is the single most important factor in hunting with anything.
I've now taken hogs with .22, 25, .30 and .45 airguns. The farthest with a .22, 16gr polymags, moving at 953fps was 42 yards, side shot between the eye and the ear...the 124lb hog dropped like he was grenaded...the pellet was found in the skull on the off-side from the shot...chipped bone on the off side, but did not break the other side of the skull...turned the brain into gel.
With the same pellet in .25, moving roughly the same speed, I've taken 5 hogs at 77-84 yards (distance to a buddy's feeder from his shoot house). 4 of the 5 were headshots...all penetrated both sides of the skull, 2 were complete pass throughs from the side shot, the other two were laying against the spine in the neck (frontal brain shots). I shot one in the boiler room, just over the heart, on purpose....he ran 60 yards before stumbling around and falling over at the edge of the woods...that pellet was found under the off-side hide...90lb hog.
I've got some Nielsen hollow Points, 29gr IIRC. They punch through both sides of 100lb hogs at 80 yards. Frontal brain shots result in pellets found in the neck/chest cavity from frontal brain shots.
The farthest I've shot hogs with the .25 Nielsen's is 108 yards, through the boiler room...took some tracking, but I found all three within 80 yards...65-120lb hogs.
With a buddy of mine's .30 Impact, anything within 100 yards is dead...he's killed over 30 now, I've killed 4 with it.
I have to reiterate, moving projectiles at speeds faster than 850fps and being able to place the projectile exactly where it needs to be is the absolute most critical aspect of ANY hunting.
Jamie