Why Drupal? is a great article by designer Nathan Smith on why he's moving to Drupal. He's written a book about Textpattern, and used Expression Engine extensively, and also mentions TYPO3.
I've snipped only this very small section on (essentially) why not WordPress, which is similar to what I was trying to get at with my Evolving Drupal UX by Building Products post:
In fact, WP is so tailored to blogging that I liken it to a yacht. It is streamlined for that particular task. It allows people with varying levels of technical savvy to get a site installed and online posthaste. Or, via WordPress.com you can skip the install process altogether and opt for a hosted blog. While a sharp focus on blogging ensures that the famed “5 minute install” will continue to be a selling point, it also means that WP at its core isn’t meant for big sites.
Note: I mean “big” from an information architecture standpoint. I realize that with proper caching plugins and a good hosting setup WP can power sites with tons of traffic and an abuncance of blog posts. While that’s all well and good, I’m interested in building sites and/or web applications that have both breadth and depth.
Continuing with the WP as yacht analogy, I’d say Drupal is an aircraft carrier. A ship that big can carry fighters, bombers, supplies, or even refugees in a humanitarian relief effort. What I see far too often is people trying to strap things onto their yachts and then wondering why they run into difficulties. Custom fields do not make for an ideal CMS workflow. I learned this with Textpattern.
from Why Drupal? by Nathan Smith at SonSpring.com
Nathan has done a great job by unpacking what "scales well" means from a design perspective. His side trip(s) into discussing major Drupal shops and focusing on a base language like PHP instead of template lingots are excellent as well.
Nathan doesn't mention Features, but it is a path forward for small or large Drupal shops to avoid having to "just" skin another Drupal site, without moving in the direction of templates.
Image for this post is the Features monster by Development Seed.