conditions or merged webhelp?

What's the preferred mode of attack for modular help: use conditions or create merged webhelp?

The product has a Core module that everyone has access to, and 2-3 optional modules. It's a very small project, Core only has 35 topics (so far, but not likely to get too much bigger), and the other modules will likely only require about 15 topics each. Oh, and there's a separate standalone app that will need to be included in the main webhelp but also output as a chm, in case that makes a difference.

Is it more efficient to just create and apply conditions at the topic level and in the TOC, or go through the process to create merged webhelp?  Probably for the size of this project conditions is the way to go, but what about for larger projects? Are there any other considerations?