[TenTec] Question about New Omni VII

[Steve Berg]

I got my new Omni VII yesterday, and let it thaw out overnight.  So far, 
I have discovered that it will not work with the Ten Tec power supply 
that has worked fine with the Corsair II for years.  But it works fine 
with my Astron.

I am confused about one of the options.  It has CWL and CWU operation.  
The last time I had to deal with this was when I was running my National 
NCX-5.  I gather that it is the lower and upper sideband versions of CW, 
but what difference does this really make? Is one preferable over the other?

I have read the manual several times, and have managed to make a few 
contacts with it so far.  After the Argonaut II, the Argonaut VI, and 
the Corsair II, I am not used to this sort of rig at all.

Help?

Steve WA9JML