Back in the good old days, there were 2 types of pistons available - cast and forged. Cast pistons are inexpensive, quiet, and offer excellent oil control due to tight piston to wall clearances. They are also weak compared to forgings, and the quality of some brands was (is) fair at best. Forgings are strong, but expensive (especially for non-popular engines like the 318). They also require more piston to wall clearance, so they're noisy (at least until the engine warmed up) and oil control isn't as good as with cast pistons. I'm a traditional kind of person, so when I set out to build a high performance Mopar 318 for my 66 Barracuda, my initial thought was to use forged pistons. After talking with the tech support folks at Silvolite, I've decided to run cast, hypereutectic pistons.
Because they're cast, they run fine with a tight piston to wall clearance, so they're quiet and have excellent oil control. Instead of being cast from old-style aluminum alloy though, they have a higher silicon content which makes them much stronger than a traditional cast piston (but still not as strong as a forging). Also, most hypereutectic pistons are machined on CNC equipment, so quality and consistency is better than traditional castings. According to Silvolite, their hypereutectic pistons are good for engine speeds at least up to 7000 rpm and are almost always a better choice for a street engine than forged pistons (which they also sell). For the Mopar 318, they are avaiable with either flat or domed tops. I bought a set of flat tops, which give a compression ratio of 9.2 to 10.4 depending on combustion chamber volume. They also have enough meat on top to take some milling to tweak the final compression ratio. I'm running 302 head castings and shooting for a 9.75 compression ratio.
The only possible down side is that they use a 5/64" ring package, while most high performance forged pistons use a 1/16" ring package. Having 25% more surface area increases internal friction, which robs a little power. However, that same 25% more surface area also (hopefully) increases wear life. For my application, I think quieter operation, better oil control, and potentially longer life is more important than extracting every last bit of power. I just want a good road car. If I was building it to street race, I'd probably go with forgings.