Mobs can't spawn on either of those things.How about the conveyor belts from minefactory reloaded? Those are a really nice method for it, That is usually what I use when I need to transport mobs around
Another possible extremely vanilla way of doing it is minecarts on tracks.
Yeah my thought exactly. The Grinder have pretty much the same range as any pushing/pulling means you can find, so might as well just kill them on the spot. If the room is more than 10 blocks across, you could just make a pillar in the middle with the grinder(s) embedded.Why not just use an mfr grinder?
Did you read anything other than the title?