I personally prefer Lowrance. The new Hummingbirds are interesting, but I don't want a transducer the size of a brick off the back of my transom. They can't be mounted inside the hull due to the side shooting capabilities, so until they address that issue, I will stick with the Lowrance.
I just installed a Lowrance 520 and it was an awesome unit.
The 2007 Navionics card is REALLY nice. Plus, they really have a good customer support network.