I have both antennas on my 396 (not the XT); the Spectra requires a good ground to work properly. If you use a trunk lip mount, make sure that the little screws bite firmly into the metal of the trunk. It's not really an antenna that has any appreciable amount of gain. If you are in an urban or semi urban area, that's actually an advantage, contrary to what you might think. This means that there's less chance of overloading the scanner with too much signal.
The Condor is a very good handheld antenna, but likely should only be used in a fixed environment - that is, the radio isn't being carried around. It's not a heavy antenna by any means, but it is taller than what you would expect. If you need something better to carry around with, I understand that the RS 800 mhz antenna is a good choice, particularly if you are interested in listening on 800 mhz trunks.
The Condor does quite well at VHF hi (I can hear the NWS transmitter in DC on it, and that's about 40 miles from me, in an urban environment), and does well at UHF as well (several companies that use the 460 mhz band at BWI airport - which is about 10 minutes from me - are easy copy).
73 Mike