The file sizes for both versions of Final Fantasy XIII-2 have been revealed. According to a poster on the NeoGAF forums, FFXIII-2 will weigh 14.446 GB on the PS3 and 7.8 GB on the Xbox 360.
Compared to FFXIII, which weighed 37.6 GB (PS3) and 18.3 GB (Xbox 36), this looks pretty reasonable.
Final Fantasy XIII-2 is now out in Japan, and will release in US on January 31 and Europe on February 3 for the Xbox 360 and PS3. Famitsu gave it a score of 40/40, saying that it improves upon FF13 in all aspects.