I don't know about the binaries, but the primary benefit of 64-bit DB2 is the ability to address more memory, especially for the bufferpools. In 32-bit, DB2 instances are constrained to about 2GB of memory (depending on which operating system), unlike 64-bit DB2 which can address just about as much physical memory as any server can support.
Whether your DB2 database can benefit from addressing more system memory depends on the amount of data in the database and the performance requirements of the application. If the total of all your bufferpools for an instance is less than 1.5 GB and your bufferpool hit ratio is already at 99%+, then you are not likely to see any performance improvement by using larger bufferpools that are available with 64-bit DB2.
M. A. Feldman
IBM Certified DBA on DB2 for Linux, UNIX, and Windows
IBM Certified DBA on DB2 for z/OS and OS/390