Minecraft: Pi Edition includes the Minecraft: Pocket Edition Touch UI. MCPI-Reborn includes a mod that enables it. This is enabled by default because the default UI has bad Survival Mode support.
While Minecraft: Pi Edition includes the code necessary for Survival Mode, it is disabled by default. MCPI-Reborn contains a mod that allows you to use Survival Mode. This is always enabled.
Minecraft: Pi Edition and Minecraft: Pocket Edition control mob spawning by game-mode. This mod makes mob spawning independent of game-mode. Mob spawning is enabled by default.
Minecraft: Pi Edition doesn't have a functioning settings menu, so it is impossible to enable fancy graphics. This means things like clouds and transparent leaves. MCPI-Reborn includes a mod to enable it. This is enabled by default.
Minecraft: Pi Edition and Minecraft: Pocket Edition both contain auto-jump enabled by default. As many people find this annoying when playing with a keyboard and mouse, MCPI-Reborn includes a mod to disable it. This is enabled by default.
Minecraft: Pi Edition and Minecraft: Pocket Edition control whether to highlight the selected block by UI mode. This mod makes it independent of UI mode. Block outlines are enabled by default.
When an item that is normally unobtainable is in the inventory, Minecraft: Pi Edition and Minecraft: Pocket Edition render a bright red background behind it. This mod removes it and is enabled by default.
Minecraft: Pi Edition and Minecraft: Pocket Edition include an additional atlas alongside the block and item atlases. This atlas contains pre-rendered images of all blocks and items in the inventory. This makes it so that modifications to the blocks or items atlases don't affect the inventory unless you also modify this atlas. This mod disables this atlas. This is enabled by default.
Both Minecraft: Pi Edition and Minecraft: Pocket Edition include code for smooth lighting that is disabled by default. This mod enables it and is enabled by default.
Both Minecraft: Pi Edition and Minecraft: Pocket Edition include code for 3D anaglyph that is disabled by default. This mod enables it and is disabled by default.
In both Minecraft: Pi Edition and Minecraft: Pocket Edition the Camera entity renderer is disabled. This re-enables it and makes the [[Camera|Camera's]] particles appear higher so they don't obscure the picture. This is always enabled.