re: set statistics time,io on ...
Hmmmm ... were these settings also enabled for the repro on linux?
All of the query-specific numbers (monSysStatement data, ULC* values, # pages written, # txns) are (effectively) identical so there doesn't appear to be any extra overhead for the execution of the actual queries ... so that leaves questions about the overhead of non-query processing.
Again, I'd suggest running your tests (Solaris; part vs non-part) with *ALL* options (showplan, stats io, stats time, etc) turned off. The objective is to eliminate the overhead (cpu, logicalIOs) required to process the enabled options.
I'm wondering if the extra cpu/logicalIOs could be related to the dataserver having to deal with 1 partition vs 6 partitions when generating the info for the various enabled options.