Keep in mind also that a heavy piston will need mallory added to the crank.
So a cheap heavy piston may cost you more in the long run after balance, then a higher qualilty lighter piston.
A heavy piston will only need Mallory metal in the crank if it's heavier than the heavy OEM piston it's replacing. 340 pistons are naturally heavier than comparable 360 pistons because 360's are shorter (compression height) due to the extra stroke.