Thanks for the reply. After more researching, reading and testing I think I’ve found a good "line" between the two or rather, what separates ModX from all the other CMS since I believe it’s in a category of its own.
My take on this is, for a site where you are going to build it around a community and have heavy community participation, Drupal and those types of CMS are the choice. Because they come with basic features for those out of the box and contain many modules for extending community and user interaction, it seems to me that’s a hands down choice.
ModX seems like it could do that too, but it doesn’t look like it was built for such a thing. Upon inspection, it seems ModX would be good for when one is building a site with dynamic content but doesn’t require a lot of community interaction such as a blog, a content site, article site, etc. Also seems like a good choice for paid developers who develop those kinds of sites for clients.
For the project I’m doing, by my definition it seems Drupal is what I should be going with. However, I am very interested in ModX and I’ll be keeping my eye on it and I’m pretty excited to build a site with it in the near future.