You are alerady familiar with pros and cons of server-side vs client side scripting. The same goes for client vs server-side xsl tranformation.
If you transform xml at server and only send (x)html to browser, you can avoid browser incompatibilities and the fact that the user might not have xml parsers at all or their browser interprets xml diffently than you expected.
Client side transformation saves server time. (Typical for data validation) For the combo box population I would say client side and only call server when you actually need to update the database. For any other changes on the fly, do it client side.
: I would like to know which XSL transformation is best. Can you give some more idea for this scenario?
:
: Now our existing application is using client side transformation, so we can able to transform whatever data to be displayed and dynamic datas are able to populate into Combo Box without hitting server. But if you are going for server-side transformation output could be HTML or TEXT of static. If you want to populate dynamic datas into combo box without hitting server, is it possible?
:
: Ex: We have two Combo Box, one is Ticket Name, which contains name of tickets. Second is Task, which has to be populated when you are selecting Ticket Name. Now we dont have server hit, so how can improve performance of server-side XSL transformation for this case.
:
:
:
: Note: I am doing analysis between Server-side Transformation and Client-side Transformation
:
:
:
:
:
:
:
To err is human, but to really foul things up requires a computer. (Farmers Almanac) 
