This is a hotly contested issue among many proficient javascript developers. Many other languages have a compilation phase where the entire program is bundled up for deployment (JBoss's .WAR files come to mind). Programmers that come from more traditional backgrounds often favor this approach.

Javascript has seen such growth in recent years that it is difficult to chart exact best practices, but those that appreciate the more functional nature of Javascript often prefer the module loading approach (like require.js uses).

I wrote Frame.js which works much like require.js, so my bias is towards the module loader approach.

To answer your question directly, yes, it is one or the other.

Most that argue for packing your scripts into a single file believe it enables more compression and is thus more efficient. I believe the efficiency advantages of packaging are negligible in most cases because: (1) module load times are distributed over the entire session, (2) individual modules can be compressed to nearly the same percentage, (3) individual modules can be cached by the server and routers separately, and (4) loading scripts only when they are needed ultimately allows you load less code for some users and more code overall.

In the long run, if you can see an advantage to dynamic script loading use it. If not, bundle your scripts into a single file.