I did a comparison between Real Estate and Properties on NameBio - and I found some interesting results. Both of which sold nearly as many as eachother (recorded publicly). RealEstate topped Properties (25 to 21). Also noteworth is that domains with "Real Estate" have had some larger sales.
OklahomaRealEstate.com - 25,000
where the largest recorded "Properties" sales was for USAProperties.com - $3,650.
However, Real Estate the keyword has many domain sales in the several hundred dollar range, where most with Properties have sold at about the 1k mark.
Are these results typical? Unfortunately the amount of recorded sales makes this too small a test group to really put a lot of stock into - but just comparing doesn't reveal some interesting results.
Justin