Yeah, you would need to look at java, too. (NOTE: I can spell java ... that's about the extent of my java knowledge.)
To rule out ASE-related performance issues you could try running the same ddlgen operation against both dataservers and then compare the monSysStatement (cpu/wait times, logical/physical ios) metrics for both.
As for statement cache settings ... enabling statement cache (statement cache size; literal autoparam=1) in ASE 15.x is usually a good idea, especially if your application(s) submit a lot of SQL statements (as opposed to stored proc calls, RPCs or prepared statements). If you don't have statement cache enabled and ddlgen is submitting a lot of SQL statements then you're likely seeing some degradation due to the extra time it takes the ASE 15.x optimizer to compile queries (as compared to the 'faster' ASE 12.x optimizer).
