The following is from Arthur Morris and copied from the birdsasart.com store page.
I had long resisted doing conversions in Digital Photo Professional (DPP), the software that comes on a CD in the box with your new Canon camera. I tried it a few times, found that the interface was not as user-friendly as with Adobe Camera RAW (ACR), and did not see any great advantages to using it. ACR was fast and the results were excellent.
When I began working with images from my new EOS-1D X, I noticed right off the bat that the colors were off and that the image quality was poor at best. Skilled photographer Arash Hazeghi had been using DPP for quite some time, often touting its benefits in the Avian Forum at BirdPhotographer's.Net.
With phone help from Arash, I began converting my 1D X images in DPP explicitly following his instructions. The images looked so good and so clean with accurate color that before long I was converting all my 5D Mark III, 1D Mark IV, and 1D X images in DPP and loving the results.
I tried DPP and the images were better, but I like the LR workflow, interface, and features. According to Arash there is no way to combine the 2 and maintain the benefits of DPP. I would like to be able to bring the RAW image into DPP and save it as tiff or png and then do all the other processing in LR but I guess it doesn't work like that.
The basic premis is that Adobe uses a generic RAW converter process that works well with many RAW file formats. DPP is tuned to work with Canon RAW files and therefore does it better.