You probably noticed in the initial video evidence strongly suggests elements of the Russian government were involved with the downing of the flight, though the targeting of the passenger plane was likely a mistake.
Given this, it would be odd to trust RT on the issue, since the Wikipedia article on RT shows that RT (formerly Russia Today) is seen by many to be a propaganda tool of the Russian government.
How did we find that information? We started by doing our "just add wikipedia" trick. Let's show the Reuters one first:
An animated gif showing the "just add Wikipedia" moves in checking out Reuters.com.
We search the URL or domain and add our bare keyword "wikipedia". Selecting the most relevant search result, we find Reuters is an international news organization. Scanning the article we note that there have been a few controversies related to timidity with climate change reporting and allegations of anti-Israel bias, but nothing that relates to this subject.
What about RT?
An animated gif showing the "just add Wikipedia" moves in checking out rt.com.
We do the same search for the URL or domain adding our bare keyword "wikipedia". As mentioned above, when we click through to the article we notice it is funded by the Russian government. Government funding is not necessarily bad, but scroll further we note that there are credible accusations it is a government propaganda outlet. In this case, read Reuters, a credible international news agency, and ditch RT.
One of the more difficult things for students is evaluating controversies on Wikipedia pages. Almost any paper of significant size and history will have controversies. So what counts? When scanning controversies quickly, it's worthwhile to look for a couple things.
First, is there evidence of outright deception or the embracing of conspiracy theories? Direct government influence? An agenda that is explicitly focused on propaganda? Things that are intentional or patterns of behavior mean more than ocassional error.
Second, if errors are noted are they related to the topic you are looking at? A paper that has published sloppy reporting on health claims, for example, might be okay on political news. And papers with biased opinion columns are often home to quality reporting. But if you are looking at a health claim and the controversies are around health, that may be a different story.
As always, stop and be strategic about your research — the question is usually whether a particular source good enough, or if there are enough questions around it that you should find better coverage. You don't have to prove RT lied about MH17, for example. You just have to read enough of the Wikipedia page to realize you shouldn't be reading coverage from state-controlled media on this issue, especially since the state in question was likely involved in the event.