That reply is the most vague, nonsensical piece of drivel I have read for a while. We should be comparing engines in stock form. The 340, hands down is the best and sweetest SB (chev terminology - lets say LA engine) in the world. Most people should know that Chrysler generally underrated their factory performance figures. The 426H was rated at 425HP but most people who have been around them for a while knew that the actual figure was closer to 470-500hp. The same went for the big valve 340 (2.02 X head). Rated at 275 hp, they have been proven many times to deliver over 300HP in stock form. In fact, I think it was one of the mags, possibly HotRod Magazine that decided to put that to the test. They built two 340 engines to stock specifications as far as possible (using stock components). One engine dyno'ed at 315 hp, the other went to almost 323hp! Quite impressive.
In contrast, the Cheep 'n Hevvy Chevvy 350 was more a lump of cast iron in the shape of an engine. Sure it could be made to perform and that was why from very early years there was a huge amount of performance equipment and upgrades available for the SB Chevs. Compare that to Chrysler - until even as late as 15 years ago there was a much lower amount of bolt on performance equipment available for Chrysler engines. Most likely (IMO) because they didn't really need much to get them to perform very well, due to their basic engineering excellence and strength.
