You'd learn a lot by building a Hemi: The intracacies of valvetrain setup, the unique (for the time) torque sequencing on the crank, how to install head fasteners from inside the lifter valley, and who makes the best-tasting ramen.
If you want an engine to wow people when you open the hood, a 426 Hemi simply cannot be beat. If you want to be the fast guy on your block, you're much better off building a 440. Hemis haven't been the fast way home for a long, long time. The horsepower-to-dollar ratio is abysmal, but most people still flip out when they see one. In fact, all my non-Mopar friends are convinced that owning one simply has to be my ultimate dream: "How can it not be?" Easily! I'm an enthusiast rather than a collector, I don't care what people think of my cars, and there's nowhere near enough bang for the buck.
We all have our own dreams. Chase yours regardless of anyone's opinion.