I downloaded the most recent release, 20130428 and tried compiling a sketch. When comparing compiled sizes, it seems CodeBlocks is creating slightly larger files. When I compile in the Arduino IDE, I getBinary sketch size: 6,724 bytes (of a 32,256 byte maximum)
And when I compile the same exact code in CodeBlocks, it saysavrdude.exe: writing flash (7660 bytes):
The HEX files are also larger, With the Arduino IDE the HEX file is 18,934 bytes whereas with CodeBlocks it's 21,573 bytes.
Looks like there's some more optimization to be done.