Difference between 7.5 and 7.8

What is the primary difference between Siebel 7.5.2 and 7.7 Versions ?

Are having lot of differences between siebel 7.7 and 7.5.2. the primary difference among them is " Symbolic strings are available in Siebel 7.7 and not available in 7.5.2". hence the future scope for upgradation like things are high in siebel 7.7.

Optimization techniques in EIM
1) Limit base tables and columns to be processed by using : only base Tables,ignore base Tables,only base Columns,ignore base Columns.
2) Always delete batches from EIM tables upon completion. Leaving old batches in the EIM table wastes space and can adversely affect performance. For other suggestions on working with batches.
3) Run independent EIM jobs in parallel. Two or more EIM processes can be started simultaneously by using the Siebel Server Manager.
4) Trace Flag Settings, using Synonyms, primary key only Parameters
Limiting the Number of Records and Rows for Merge Processes.
like this many techniques are there which will optimize the EIM process