I use the Command Center which installs the appropriate version for the OS. There should be a switch at the beginning of the install process to set which version to install. To see the install options using the Command Center make sure to have the current version installed from
http://www.cakewalk.com/Command-Center and enable "Verbose Install" on the setting page. As I mentioned above, I do not bother with 32bit installs so have not tested the 32bit installation, programs or plug-ins. It is possible to have both 32 and 64bit versions of any Cakewalk DAW installed on the same machine. They will share some configuration such as the user directory but programs and plug-ins install in separate directory trees.
Memory available to the program is the principle advantage of 64bit processing. Also I believe the 64bit versions are tested more thoroughly. Years ago, when 64bit was new, the 32bit platform was the main test platform. This changed around 2010. That said, when working with legacy projects with all 32bit plug-ins (especially DirextX format) a 32bit install may be necessary.