a big thanks to toops and Puddin' for proving the original information for this topic
Basic info:
What are Power Discs?
Power Discs are a supplement to your characters and gameplay in Disney Infinity. They are sold in blind packs of two and can be placed on your Infinity Base to enhance your game.
What is the difference between Hexagonal and Circular pieces?
Hexagonal pieces unlock assets to your toybox, such as a new dome/environment to have and create it or new mounts/vehicles to ride. These are placed on the hexagonal spot on the Infinity base.
Circular pieces are character enhancements, such as enhanced attack power, movement speed, or increased money gain in play sets. These are placed underneath a figure on the base.
Circular Discs
Scrooge’s Lucky Dime – (DuckTales) – Economy Boost - In-game character has a chance to gain economy at a faster rate.
Merlin’s Summon – (The Sword in the Stone) – Pickup Range Boost - In-game character’s range to absorb pickups expands.
User Control – (Tron) – XP Boost - In-game character has a chance to gain experience at a faster rate.
Zurg’s Wrath – (Toy Story) – Melee Damage Boost - In-game character has a chance to deal extra damage.
Damage Increaser – (Cars 2) – Weapon Damage Boost - In-game character weapons have a chance to do more damage.
Hexagonal Discs
Hook’s Ship – (Peter Pan) - (Mount) - This vehicle is perfect for one-handed airborne pirates who like to cackle.
Hangin’ Ten Stitch with Surfboard – (Lilo & Stitch) - (Mount) - In-game character gets a hover surfboard with Stitch on the front of it inside the Toy Box.
Mike’s New Car – (Monsters University) - (Mount) - Drive Mike Wazowski's car inside the Toy Box.
On The Grid – (Tron) - (Skydome) - Make the sky in the Toy Box themed to the "Tron" film/cartoon.
Tron Interface – (Tron) – (Textures) - Make all of the terrain objects in the Toy Box themed to the "Tron" film/cartoon.
NB: The power discs User Control, Hook’s Ship, Hangin’ Ten Stitch with Surfboard and Mike’s New Car are also available as standard non lenticular versions in Series 2.