So here's the deal; really good renderings are made by people.
Image by Marcelo Souza
Yes, of course the software and tools you use play a significant role in the final product - but I've seen works of art produced with freeware and I've seen garbage come of out pricey, top of the line software. I've learned not to bash certain engines because they're free or simple, and I've also learned not to expect my images to be gold just because I use X instead of Y. There will always be people who have the talent and technical mastery of a given piece of software to make something elite.
So why try yet another tool? Shouldn't I just master the one I currently use?
Image by Ludvik Koutny
What is Corona?
Image by Duncan Howdin
Right now there is a decent amount of hype around Corona Renderer - a CPU based stand-alone engine impressively written by one programmer, Ondra Karlik. It also now has full integration into 3DsMax with C4D integration on the way. You can even download conversion scripts to easily convert existing Max scenes. Because it's still under heavy development, you can download the BETA version of this engine for free simply by joining their forum! [Side note: if you don't use Max, you can still use Corona in its stand-alone form - a couple steps described in this arcitle.] If you participate in the BETA now, you will automatically get the commercial version once it's out!
Why try Corona?
Image by SDH
Admittedly, I know nothing about coding and the algorithms that go into rendering engines...but from what I can tell, the reason Corona is worth checking out is that it supports both Biased and Unbiased rendering methods.
In a nut shell, unbiased rendering means that their algorithms ensure photons will be distributed everywhere - accounting for all possible light, granted you let it run long enough. In other words, if you let an unbiased render run on (length depends on the scene) it will eventually converge on the correct solution. Maxwell and Indigo are two examples of unbiased engines - which claim to be "physically accurate". The down-side of unbiased algorithms is that to ensure total photon distribution, a frick ton of extra noise is introduced, and could still exist in the image even after hours and hours of passes.
This is why Corona also has a biased component - which make concessions in the interest of efficiency. Biased engines use a sample bias (hence the name) and subtle interpolation/blurring to save on rendering time. VRay is a biased engine but offers a hybrid depending on your primary and secondary GI selections. The Chaos Group provided a super detailed explanation here. So the artist has more control over biased engines and can still achieve "physically accurate" looking results - granted he knows what he's doing. Biased renders are typically better at animations, film, and motion graphics due to their efficiency.
Unbiased renders are supposedly better for stills and ArchViz (large scenes, usually lots of illumination), and since I rarely do animations, I'm excited to give this a try! I'll post some images once I've learned my way around the software.