One difference I notice is that the DNG file doesn't preserve a few of the Canon specific details- like showing where focus points were used. Besides that, I don't notice much of a difference.
There are now THREE flavors of DNG.
One which embeds the entire RAW file in it with all the raw information in addition to the edit info.
One which embeds only the edited image(This is the one most are discussing here)
One which embeds the edited image with lossy compression, but not as much as jpeg. It might be better than saving jpegs? Its new and can be tested in Lightroom 4.
You can take your choice.