Provided you're building something short of an all out competition motor, there's alot to be said for the current generation of high silicone "hypereutectic" aluminum pistons. They have almost the same thermal expansion rate as the cast iron blocks they run in and so normally exhibit better ring seal than a comparable forged aluminum slug which has to fit a bit looser in the bore to account for the large expansion rate difference between the piston alloy and the block. These pistons are also quite strong, and weigh much less than the old school cast or forged steel slugs Detroit used to use. Hence, less reciprocating mass and better throttle response. If you're building a blower motor, or a motor that will regularly ingest more than a 100 horse shot of N2O, or a wild street strip motor that runs 10.0:1 compression or more, than the added strength of a forged piston and polished or H beam rods and quality rod bolts is probably a good investment. In this case, the added peace of mind is worth some sacrifices in the area of ring seal. Otherwise, a quality cast hypereutectic piston will give your pony many miles of quality service.
'66 candyapple red coupe, 347 4v engine, performer RPM heads and intake, 600 cfm holley carb, Sanderson short tube headers,
T-5, Versailles 9" w/ 3.50 gears and a detroit locker, 4 wheel discs.