I think that it is more important to concentrate on the content of your mail piece rather than the form it takes - Make it BENEFIT driven.

I would concentrate heavily on networking.  

If you go this route you’ll need hundred of letters likely to get one deal or have a concentrated list and mail that same list a lot of times.As most people will tell you, when I get a letter like this I throw them away, so you need a lot of letters

For me, my business has been concentrated in certain areas for a few years and we now manage a little over 2100 properties.  

320-acre development set to take off by airport "The city of College Park is launching a $500 million-plus mixed-use development on 320 acres, with potential to create thousands of jobs and representing a major step in making the region’s “Aerotropolis” vision of concentrated development around Hartsfield-Jackson Atlanta International Airport a reality.The development site is on the north side of Camp Creek Parkway, west of Interstate 85 and Hartsfield-Jackson and across from the Georgia International Convention Center.

I can use that time and money to concentrate on growing my real estate business.