[SunHELP] LOAD metric for uptime and top

I'm trying to figure out why my 1st server (6cpu E3500) has only 10% cpu
utilization and no iowait has a load of 1.2, yet my 2nd server (2cpu
280R) has 23% cpu utilization and no iowait yet has a load of .5 via
uptime and top.  From consensus, I understand the 'load' value doesn't
necessarily tell you an absolute value of whether a box is busy or not.
However, I have a hard time explaining it technically to the other
developers and system administrators.  Can someone please give me a
technical answer on how the load metric is calculated and why we're
seeing higher load on our less utilized box, vs lower load on our less
utilized box?  TIA