Drupal vs Magento for Ecommerce Websites
Drupal is a good and secured CMS system with few plugins ( UberCart, Drupal Commerce) which can be used to as eCommerce store . Magento is superb and robust eCommerce platform so it can't be a CMS, but it have ability to add CMS pages from backed and link to navigation using blocks and phtml files. Lets see where Magento Scores well over Drupal. Drupal has a very popular e-commerce solution Ubercart which is comparable to Magento.
First when I look at Store Adminstration, Magento is better. You will have a learning curve if you are working with Ubercart. Magento has a simple unified interface for managing the entire store. To deploy products to your store there is a wizard like interface while Drupal has the concept of adding pages for products. Magento is great platform for e-commerce, has great options to manage products, prices, taxes and so on.
The question then is really about the scale. If you want a simple store with few products then Drupal is a good solution Or Joomla+Virtualmart as an option. Magento needs more resources and hence more hadware and hosting costs, also opensource has limited features. With Drupal you can leverage from the modules for SEO and get good rankings. Metatag, Search404, Global Redirect, XMLSitemap are some of them to be named for SERP.
Magento is famous for the number of functionalities it offers. It has extensive analysis, report and product management systems, mobile version or the payments system. Script allows for running several stores at one time from one administration panel. Another example of Magneto's extraordinary capabilities is the ability to set a template for a given product that will make this product to present to a client differently than other products at the same time period.
You can't have a good support without a large community of users who, among others, contrubute to discussion board and Magento's technical support is very good. So its easy to say Magento is better for e-commerce in the present circumstances.
Now lets compare to the aspects where Magento Lacks and Drupal Scores
When you need CMS functionality along with Ecommerce store then you will need to reach out to Drupal Commerce. Magento CMS functionality is pretty limited. Given the importance of content marketing for driving content to your site, ecommerce platform needs decent set of content management/marketing tools.
Magento is restrictive in the way it's time consuming to customize. Plus finding people who REALLY know how to work the back end can be difficult . Magento is really poor for everything else not related to product listings. Lack of CMS features / Lack of promotion features / NO search engine / etc. Main benefit of Drupal CMS itself is an opportunity to add, modify and manage content in a simple and effective way. Drupal has huge number of extensions and can be customized the way you need
Post Panda/Penguin/Hummingbird updates of Google Algorithm, content marketing is king. The community edition of Magento lacks the tools you need and Drupal Scores well here.
Drupal is free and there is no concept of "paid module"and the community at large is very good at supporting these modules with patches and improvements.
If learning curve is of concern then you can try out Drupal Commerce using a pre-configured Drupal Commerce platform called Kickstarter(check out the website to find it). It's easy to install and comes configured ready to go. I don't recommend you use it as the base platform to build your own site with, but it's a great introduction to the world of Drupal Commerce.
Drupal Commerce is a much better GUI for Site Admins. Hosted companies like Shopify or Big Cartel succeed as the site admin features are easy to use.
Drupal does large scale websites very well. You'll need a decent server infrastructure to run it, but it can handle a lot of traffic with ease. With Ecommerce Sites, server performance to a huge factor. Pantheon or Acquia provide great hosting as they optimize their servers deliver the best experience (Varnish, Redis, MemCahce, SOLR Serach, etc.). If you dont have a good hosting the Magento Performance can become horrible on shared hosting especially when you achieve scale and huge traffic.
How do you make a choice between the two. Whether to choose Drupal or Magento ?. One thing I would recommend is to try out both of the systems for a week and then decide. This time is well invested if you are thinking long term. There is no best solution or nothing like one size fits all. I know people who have switched to Drupal after trying Magento and vice versa.