I have used Striking MultiFlex, Enfold and Avada. I dont have experience with the others. Here is some thoughts from me. I have more experience with Striking of the three, after using them all it is my preference, but I shall try to give balance to my thoughts:
Longevity - Striking is the oldest of the themes, and I think has the best record of updates, having updated at an average rate of 1x a month since released in 2010(?). They advertise that whenever anything updates (wp, browser, wpml, etc) they automatically update. They also have a really excellent record of adding user suggestions over that time.
Striking is world famous for its support which has been writeen about widely and they operate an open forum which is very rare… Kriesi also is extremely well known for support. I did not like the Avada support but it could be the timing of when I was using it, but I think it is not as good as the others.
User Rating - Enfold is the winner here, by a fraction, over Striking. The high ratings these two enjoy reflect the quality of the themes. I suspect that had Striking been released recently it would have an even higher rating - it came out at a time when the rating system was in infantcy, and not widely used by buyers.
Backend - This is very difficult as some of these themes are built on different basis from each other. All these themes advertise as multipurpose and customisable. The one with the most actual theme settings for these is Striking, by a long shots. It has 13 different panels, with hundreds of settings, just for the purpose of setting defaults for everything. That is much more then I have ever seen in any theme, not just at Themeforest. Then it gives you the ability to override all the settings, either in a metabox attached to the page editor, or in a shortcode, so you are never limited by the theme default.
This large array of settings dwarf what is found elsewhere in my experience. So if desiring to customise, this is hugely advantege over the other choices. I add that although Avada advertises new page option controls they are nothing compared to Striking. I have to go look at Enfold again for this - my last use a few months ago they did not have much for page specific options.
But it can also presents a challenge. The Striking developer has not wanted to do skins as they feel it constrains design flexibility according to what is posted on there support forum. All the other themes have skins, which while taking away at least some choice (all choice in some cases), does make it easier to have an instant alternative preset layout. Harder to customize and sometimes cannot be customized at all without big difficulties, but definitely easy to start with.
I think there is also philosophy at play. Some of these theme are driven by using a page builder of one sort or another - Enfold & Jupiter, the others shortcode. Page builder designs work differently. If you like using the visual editor, then a page builder design might be the first choice. Page builders have limitations (part of reason I stopped with Enfold) and not everything works correctly, but enough does for most purposes that it does not effect most sites most of the time.
So if you prefer page builder, and do not want to pay for the plugin at codeconyon, then Enfold or Jupiter - you would have to choose between them - I believe Jupiter is likely on par with Enfold or very close to it but “artbees” is not quite as well known as Kriesi, who is a well deserved wp legend.
I do not use the Visual Composer, but it works fine in Striking. In fact almost every plugin works in Striking and that is one of the things I like about it. I have less experience trying a large number of plugins in the others, but one reason I left them besides the less custom abilities was plugin issues. This may have been fixed for them since then, I do not know.
Mobile - you did not mention this, but it is very important. And this is where the pros and cons perhaps are most difficult. All these themes other then Striking are Retina ready immediately, whereas Striking requires the retina plugin. Enfold has wider page and sections. Very nice feature (you have to check Jupiter & Inovada but I recall at least one does have this).
Unless a recent change or I never notice, Striking is the only one with responsive text shortcode, and able to do content choreography properly. And it has the most mobile fallbacks built in as settings for theme functions and post options. I would call Striking a mobile first theme or very close to it even without retina. I think it mobile performance is the best of them all, as everything in it works in mobile and you can lay out a page to appear different even in a mobile viewpoint. Content choreography is the big test of a true mobile theme. Its not much talked about, but once you learn how to do it, it is really great
This is long comment so I will stop here. I say the best part of Themeforest now is that there is many quality themes to choose from and your group of choice support this. My overall recommendation is Striking MultiFlex - which I think also need to update there demo to show all it can do: wpml, rtl, any ecommerce plugin, responsive options, more videos (they have some videos but a large amount of help documentation which they complain no one reads, I think documentation is the past now and video is the new help option of the world) . But all your choices are good and you can assure of building a nice site with any.
You did not mention ecommerce. So I did not speak to this matter. For ecommerce definitely Striking. It has customisations which work with many ecommerce, not just woo.
Hope this helps. It is my pesonal feelings from building sites. I believe it will come down to your purpose, and what features you value and will need the most. There is certainly no wrong choice. Cheers!