I own/use a TX-100 with a TX-40 as my back-up. Very happy with it.
I just bought my first camera this past weekend and haven't tried it underwater yet, so I can't really comment on bubble interference when it comes to photography. That being said, the exhaust "T" seems wide and I don't notice bubbles getting in my face.
I don't think you will go wrong with either model. Personally, I don't always like buying the "latest and greatest" model....since these are the ones most subject to recall. The TX-100 has been around longer...thus it is more of a "tried and true" model.
Other things to look at: look at the first stages as it relates to hose routing. I think they are pretty similar, but it's worth looking at. How do the purge buttons feel -- are both easy to use? If you were to be sharing air.....do you want a smaller second stage (I donate my primary) or slightly larger? Are there any differences in the adjustment controls on the second stages?
Good luck!
-Chris