I've learned the hard way to "Sell what you have". The complement to this proverb is "Install what's available". With that in mind, I would install the Compose switches. They are the best unit with a proven track record.
Yes, UPB, Zwave, and Insteon have the potential to be better systems, but they are all too new to have a reliable record. If you are a DIY type and have the time to futz around and install a few switches at a time, then any of the three might have possibilities. If you want to get in, do the installation, then get out (and not go back for service calls), then you should not be an early adaptor. The electronics industry is too full of missed delivery dates, overblown marketing hype, and equipment with hidden "gotcha's".
If, instead of from an installers POV I looked at the question from a homeowner/DIY point of view, then I probably would go with UPB. So far, none of the Zwave switches "do it" for me, and Insteon has not been released yet.