Looking to purchase a satellite radio.  I am trying to determine the
best choice between XM and Sirius.  I understand the pricing
differences, and they are not my concern.  What I'm looking for is a
more intangible measure.  I'm remembering back to the Beta/VHS days --
I don't want to buy a format that will be obsolete in 6 months.

The two systems offer many of the same channels or streams.  But I'm
more concerned about the channels they don't share.  So what I'm
looking for is information on which system new broadcasters are
choosing, and why.  If a broadcaster is choosing one over the other
(rather than both) is there reason to believe one may become the
industry standard, while the other fades away over time?

In other words ... I'm looking for what the industry atmosphere is
regarding which system will go the way of VHS and which will go the
way of Beta, and which system new broadcasters are more likely to choose today.