The 12F629 is almost exactly identical to the 12F675 - the only difference is
that it does not have an ADC.
In all other respects they are the same device i.e. 1k of program words (also the same as the 16F84), 64 Bytes of RAM and 128 Bytes of EEPROM.
The PIC12F675 and PIC12F629 are packaged in an 8 pin DIL making them very useful when you need to save space. There are several projects on this site for the PIC12F675 and those that do not use the ADC will run in the PIC12F629.
Note: Even though the PIC12F629 is small in size it has useful internal peripherals and with the ability to re-program the flash memory you will be able to develop many different projects.
[Source microchip datasheet]
For a summary of each peripheral block click here.