Sitemesh or XSLT for layout

I am designing a layout for my crm project now.
Now i am ended with 2 options one is sitemesh to define the layout or XSLT to define a layout.
Sitemesh will run at runtime from the server , it wont cause any issue if the number of request is high?
I guess XSLT will run at the browser based on the Xpath , is this correct?
Which one is better to use?
Please help me
Thanks