With nsd7x probably not much of a difference speed wise. With nsd8x and Tcl 8 bytecode compilation, it's my understanding from past threads on the AOLserver mailing list that one reason Kriston (of AOL) recommended against .tcl files under the page root is that nsd8x does not retain the compiled byte-code version like it does with .adp's and with the private and shared Tcl libraries. So you'd have a (slight?) gain from having procs in your servers Tcl library since they wouldn't have to be re-byte-code compiled each time they were accessed.
I'd suggest you structure your code so that it's clear and easy for you (and others you work with) to understand, maintain, and extend. CPU cycles are cheap in comparisons to peoples time.
