Hi guys. I am here because I am also spectating things about these two.
I am a 1year experienced developer and a quite new in web programming but I am quite familiar with these. First of all, we should not limit ourselves within these things. Everything we develop and build are based on it’s functions and features. So, choosing the best one who can handle much or better of your feature and functions will suit you.
They are both secured because they are maintained both but in terms of range or variation, it may vary. Depending on internal modification of a developer will do within these two. Sometimes, a developer may break some of the things that can lead to a leak especially of you prefer to do it in a hard way.
In my perspective, Drupal is essentially built for more coding things thus mostly intended to hard code developers. Then Joomla is leveling depends on what you want from it. The case of Joomla, if you want some extra things you want, some of it’s features and function modules are bundled commercially which means you will buy them for you to use or build your own. Unlike Drupal, some of the common functions are available for free and well maintained. There are features that are already available on Joomla and so with Drupal. That’s is why you better check their availability and convenience based on your planned website.
3. Popularity ( more work available )
They rival mainly on popularity, by counting sites by most used from both of them. They actually vary in some genres. There are many small sites or simple sites which uses Joomla because of easy administration and you can really built one for just an hour unlike Drupal, if you don’t focus or give out your full understanding on administration then you will be really frustrated but it’s just for the beginners. It really depends on what functions or features your site will require.
4. HTML5 and CSS3 support
I don’t have much info about the HTML5 from both of it but in CSS3 support from them. They both support CSS3. It was just the matter of design you implemented on both of them and with regards to the per-browser compatibility and support for CSS3. CSS3 mainly depends on what browser or media you are using.
5. Ease of upgrading from one version to another
Both of them are upgrade friendly because both of them gives out fairly understandable upgrade documentation which greatly help the users to understand what the update will be and what are the changes covered. If they do huge updates which will greatly or slightly affect the whole system flow, they introduce it in more understandable way just like when Drupal 5.xx upgraded to 6.xx and like 6 to 7.xx respectively. Joomla also do the same thing.
6. Community support
Well..Community support greatly stand out Drupal because due to it’s huge community of developers sharing their ideas, works and masterpiece for free*. [There are also commercial services and modules]. Joomla has very small community which really strains new users on understanding what to do if they want to know something because mostly, even I tried it. Some threads on their forum threads are done with private discussions which also sometimes can cost you some service charge from them. They don’t usually share some things inside the community of Joomla. They took it as an opportunity to grab on. That is why some of the Joomla expansions/modules/components/plugins are commercial, if not, it has very limited features which will make you also think of buying the whole pro version of the expansion.
This is just what my opinion is, I may have said some thing you are offended, you can comment or reply for it nicely. I just want to share my ideas about these two.
Btw, I do programming using Notepad++ only today. I probably look for some easier technique sooner or later. I build templates for Drupal, WordPress, Joomla and Moodle hardly coded but also relevant and based on it’s default content model.