Don't hate on Lightmass. It's pretty amazing. I'm sure CE3's GI beats it since it's in real time though.
CE3 GI is one bounce only tho (Can I even talk about this? ), whereas on Lightmass or The Beast, you can render various light bounces, having realistic color bleeding throughout your environments. But their not realtime, of course.
I have actually done some evaluation between the two and they are pretty much comparable. There is no obvious difference in quality or feature set.