Good question. It depends on a number of things, including the throughput of the disk controller(s) on your server, and the performance characteristics of your disk array (cache, etc).
Very few people would only have one disk (spindle) since some sort of RAID is pretty much standard these days. A single mount point might be spread over multiple spindles without you knowing about it. For example, a sophisticated SAN product with cache, and fiber channel host disk adapters on your server probably would benefit from multiple containers if you were doing huge amounts of I/O.
But if you really did have only one spindle, then probably no benefit. If you have an OLTP system with high bufferpool hit ratios, the it even makes less of a difference.
M. A. Feldman
IBM Certified DBA on DB2 for Linux, UNIX, and Windows
IBM Certified DBA on DB2 for z/OS and OS/390