SYC vs. ASE database interfaces

My client recently upgraded from ASE 12 to 15.7.  (Yes, finally.) 

Is there a discussion somewhere of all of the differences between the SYC and ASE interfaces?  The only note that I found in the documentation is that ASE interface supports 128 character identifiers.  Is that the only difference? 

I'm particularly interested in any performance improvements that may accrue to the ASE connection, as our performance was degraded by the upgrade.

We're using PB 12.5.2.5609

Thanks - Jeff