In my experience, I found that the new DPP that came with the 6d has reduced its performance.
Previously, when I had small jpegs + raw files, its "quick preview" functionality would be... quick.
However, now when having small jpegs + raw files, it's "quick preview" functionality is limited to slow poke render of the raw file while completely ignoring the small jpeg.
I now have python scripts to separate the raws from the jpegs (into another directory) and then I quick view with jpegs and delete crap images. Then, I run another python script to erase the raw files that have no corresponding jpeg.
At least I have a work around that isn't importing to LR just to quick view and delete crap images.