The primary difference between the two is the crown thickness, the N/A unit having a crown 0.200” thick and the forced induction unit having a crown 0.240” thick.  All forged pistons have the following features:

• Superior near-net shape, tight grain aluminum forgings
• Piston-to-Bore clearances similar to that of regular cast aluminum pistons
• Premium piston rings, 0.812” diameter wrist pins and wire lock pin retainers included.
• Fully balanced out of the box.  Balance across set is better than +/- 1g.
• Ultra flat, highly finished piston ring grooves
• Exceptional manufacturing tolerances for all diameters and compression height
• Radial Anti-Detonation Grooves (above 1st ring)
• Pressure Accumulator Groove (between 1st & 2nd ring)
• Pressure fed oiling of the wrist pin
• All forged pistons available with the latest in anti-friction & ceramic heat barrier coatings.
• Two choices of wrist pins, the standard item weighs 95g and the premium pin weighs 83g

Choosing your piston:
0.200" Crown
You should choose this piston if your engine is naturally aspirated or you don’t plan to run a high boost forced induction setup (10psi max).  13 grams less piston mass than 0.240” crown.
0.240" Crown
You should choose this piston if you’re running a high boost forced induction setup (up to 18psi).  This is also the piston to choose if you’re concerned about any detonation occurring, as the thicker crown will prove more durable.