hemi advantage?

If you do some good research, you will find that the only "true" Chrysler Hemi was the first generation Dodge, Desoto and Chrysler engines beginning in 1951. Even the 2nd generation 426 heads are not considered as much of a Hemi design as the original. It is even arguable that the new Hemi is even a Hemi at all. There are lots of articles and information about it. Just because plug wires go through the valve cover does not make an engine a Hemi. It has to do with the combustion chamber shape, valve arrangement and spark plug position.

But yes, ALL the engines Chrysler gave the Hemi name have several advantages, regardless or the "Hemi or not" argument. The biggest being the shape of the combustion chamber and the fact that the chambers are all finish machined. Unlike conventional wedge chambers that are "as cast" and have tiny bumps that do not allow even heat distribution, the finish machined Hemi chambers are very smooth, promoting an even burn and lower combustion temperatures, allowing efficiency to go up. They can even run on a lesser octane fuel for the same given compression ratio as compared to a conventional wedge design like a big or small block.

Also, with the intake and exhaust valves right across from each other, the air and fuel mixture has a very straight, unobstructed path into and out of the cylinder. All of these things add up to a much more efficient cylinder head and a more overall efficient engine.