"A shift in improving investor sentiment across the office sector is really a function of the fact that apartments are sort of yesterday's story. They're overbought," warns Roschelle.
Analysts at Reis also warn that supply in the apartment sector is coming fast. They estimate 70,000 units to come online in 2012, double the rate of 2011, and around 150,000-200,000 in 2013.
"While this kind of supply growth need not push apartment fundamentals back into contractionary territory, it is important for individual investors to consider how greater competition in specific submarkets caused by the proliferation of apartment rentals will impact their property's or portfolio's performance," notes the Reis report.
--Written by Diana Olick at CNBC