I have read through this thread with some interest as I have both engines. It seems that there are some here who are trying to convince themselves and others that the 440 is "as good" or even better than the 426 Hemi. I have owned a lot of 440's over the years and they are great engines to be sure (still have one in my 70 Challenger RT). However, it is very hard to deny that the 426 Hemi was/is a monumental (in terms of size and reputation) engine. Sure, in street trim the 440 6 pack would pull the Hemi for awhile but then the Hemi would begin to breathe and it was over.
I really do not think it is a fair comparison to pit them against one another, they are different animals, made for different reasons. There is no doubt that the 440 is a fantastic engine and was used in almost everything which speaks to its versatility. The 426 Hemi is a legend made to dominate the race circuits and excite the buyers.
It would be relatively easy to compare them side by side, but why? IMO they are different tools for different jobs. Additionally, I do not think it is useful or even appropriate to state that the 426 Hemi is "better", I do not think that it is necessarily better, it is more desirable because of its relative rarity. It has a huge ascetic advantage due to the huge valve covers, however from a performance level, unless they both completely stock and unmodified it is not a fair comparison. I would say this, I do believe you can make more power with less work on a 426 Hemi, but I also believe a 440 is much more forgiving and cheaper to run and maintain.