I use both. I like 3Delight because it's very fast and I can use texture preview to get an idea about my scene. Texture preview is fast and smooth. I see a lot of lag with iray preview. Shader controls are pretty good. Once 3Delight optimizes the images, the render time for added frames is blazing fast. 3Delight doesn't rev my cooling fans, and I have a better feel for the lighting model. There are drawbacks: No true HDR, no glows, no light-shedding surfaces, no radiosity or fancy lighting effects without extra effort. Iray does all that, but it places more stress on graphics hardware. I think 3Delight can do more of that, but not in Daz.