For a quick concept sketch/ quick rendering, photoshop is definitely better/quicker than a vector rendering. But there is definitely a place where illustrator rules. Personally I wouldn't use it for rendering, only lineart and logo type stuff, but for some things it's worth the effort (like if the director is the type to make constant changes, etc). You can really dial in the shape and transition of every shadow /color blend in a way that you pretty much have to do manually in photoshop or with a lot of pen-tool drawing which is the same thing you're doing in illustrator except you'll have more output options from illustrator. Check out www.techvector.com
, under portfolio, and then realistic. Those are all illustrator and as complicated as they are, you could probably make changes to anything in there (shading, highlights, colors) pretty effortlessly.
Pretty much, there's a time and place for everything, use what works best and fastest for the desired result.