You cannot deny that the small block is inherently a more efficient engine...the LA heads were designed several years later and feature angled Plugs, a better valve angle and valve centers that open on the bore centers. It also features a raised cam which allows for large strokes and reduced cam oil windage. The port cross section of a 340 is roughly only 12% smaller than that of a 440, a motor that is 25% larger.
It's "weaknesses" are few, the 4 bolt per cylinder head clamping and it's akward 59 degree lifter angle causes the pushrod to move in an arc so it's inherently less stable at high RPM.
That said, in terms of efficiency, if you pick any reasonable horsepower per cubic inch criteria up to about 1.35hp/cube the smallblock typically wins hands down, ex: it's easier to produce 340 hp from a 340 than it is to make 383hp from a 383.
When we move to the stroker realm and we include AFFORDABLE upgraded LARGE PORT heads, the Big Block (by virtue of the early Ramchargers skunk works developing the Max wedge) the big block clearly pulls away. The small block Mopar is years if not DECADES behind the Chevy and Ford market (both have heads in the 380-400cfm range) in terms of affordable bolt-on race ready heads, the magnum opens up the geometry by getting away from the rocker shaft, the POTENTIAL is there but it is still untapped.
my
i don't really like small block Stroker RACE motors, for any reasonable money investment there is a diminishing Hp/cube return once you get up around 390 or so cubes, when the piston speed goes up and the rod ratio goes down you really need a surplus of port....Fords with the multitude of Windsor/cleveland and especially the CHI Hybrid heads have the advantage above this CID range...And even still I prefer to build all my small (stock)block strokers as moderate RPM torque motors, basically lightweight replacements for OEM big blocks which is the task they fill the best and most economically. PISTON speed and ring drag go up astronomically above the torque peak and this acts like a brake as far as the flywheel is concerned, that's why (and as I tried to explain in another post) even though the HP goes up past the torque peak, the RATE OF ACCELERATION of the crank begins at that point to slow. Keeping the torque peak in the big fat middle and keeping the peak HP RPM in the moderate piston speed range is really the most EFFICIENT (in terms of longevity and heat) use of a smallblock (or bigblock) stroker, just gear and cam accordingly. A 3.79" motor with the same heads and valvetrain that can support the higher RPM required can typically make right at the same power as a 4 incher....less piston speed = less frictional HP drag, there's a reason 500" Pro Stokers run huge bores and short strokes and can make nearly as much power as the 800" IHRA motors...
All out race blocks and W9 heads are really in another $$$ league, the power is there...but the HP per $$ spent really goes up tremendously.
(how's that?)
. Time to go wrangle them up and teach them a lesson... 
