We are having below mentioned systems and client. Is it a good practise to have client specific transport route configuration. Also is there any disadvantage with client specific transport route configuration
DEV - 4 client
QMS - 2 Client
PRD - 1 client
Anyway, you can refer to notes #313991 and #556734 and to the following links for more information on this topic:
http://help.sap.com/erp2005_ehp_03/helpdata/EN/44/b4a09a7acc11d1899e0000e829fbbd/frameset.htm where you can dig into the topic "Choosing a Transport Strategy" for example.
If this information is not enough, please specify what are you trying to achieve exactly.