He means manifold vs. false bottom.
Manifold = less efficient and dependent on grainbed depth to create even flow and higher efficiency. If it's designed right and has 4 or 5 pipes correctly spaced (see Palmer's www.howtobrew.com
) it can be plenty efficienty. It's cheaper, made from copper or cpvc and is the easy solution for square, rectangular, or other non circular shaped mash/lauter tuns. Don't bother soldering it together.. it's supposed to leak, that's why you drill holes or cut slots in it.
False bottom = easy solution for a round cooler. Maybe a good choice for someone whose starting with partial mashes and will likely have a fairly shallow grainbed depth since they're not using much grains. Depth does still matter though, too shallow and you won't get much filtering and will be stuck with cloudy runnings (bad). If you're not a do it yourselfer then this is the easy but expensive store bought solution. Remember, the drain pipe should be located under the middle of the false bottom to promote even flow. If I recall correctly I think false bottoms are more prone to stuck sparges than manifolds.. but I've rarely had stuck sparges and they're easily fixed by a bit of stirring or blowing into the drain hose.
So, what do I have? A copper manifold and it works great but there's definitely nothing wrong with a false bottom.
edit: bags are for steeping. I wouldn't call it a partial mash if it's done in a bag or colander (no offense to you colander users). And I don't want to start a debate about steeping vs. PM... yeah, I know it's technically a PM if you hold a mash temp and expect starch conversion from your grains.