I have run both OCN 6 and TT6. They are both nice programs, but OCN 6 requires a bit of tinkering (you must manually install the sys.txt fix), as you must manually pair the bluetooth before you start the software, whereas TT6 automatically starts it.
Some quick observations:
TT6:
TT6 is far more user friendly and easy to use.
It works out of the box with no tinkering
the new version 6 is very cool, and has a new desktop component
has seamless US/Canada maps
has more voice choices
has tons of POIs
can be installed on CF or SD
works with the x50v and the x51 series
turns the bluetooth on automatically
navigate to contacts
OCN6:
You must manually install the sys.txt fix in order to get it working properly
doesn't turn the bluetooth on automatically
has a sophisticated user interface that, while not intuitive, has many features. These many features, however, can slow it down a bit.
great graphics
seamless US map
30 day return policy
tons of POIs
navigate to contacts
I reviewed OCN6, and you can read it
here.
Overall, I would say that they are both excellent. OCN has more features but is more complicated to use and doesn't connect to the bluetooth automatically. TT is faster, can be loaded onto your existing CF or SD card, and is more streamlined. You can't lose either way.