Over time, the functionality of dbeng and dbsrv has been drifting apart. In Version 12, for example, the new dynamic multiprogramming level (-gn) tuning feature is disabled in the personal server.
That difference is NOT listed in the "Server differences" Help topic http://dcx.sybase.com/index.html#1200en/dbadmin/da-running.html
Are there any others?
This is an important question since a SQL Anywhere engine can be run in standalone mode (one or zero actual client connections) but can still have extreme performance requirements; e.g., many simultaneous internal connections from events and services, many batch-style queries, and so on. The choice between dbeng and dbsrv is NOT necessarily a choice between "personal" and "network"... not any longer, not with the feature drift.
...or is the answer, "Always run dbsrv unless you have a good reason to run dbeng"?
Here's another difference, not performance-related: The default permissions required to stop the server using dbstop are different: dbeng -gk all versus dbsrv -gk DBA.
This is not (yet) an exhaustive list - I will add to it when needed.