As you say, that's a difficult question to answer - most of what I would say about the 320 has already been said in this thread...(even though it was discussing tabletops, it's still valid)
http://www.radioreference.com/forums...ad.php?t=59441
You are quite correct about the antenna being the other side of the equation here. A lot of folks use active antennas- and unfortunately don't use them properly. The better ones have an adjustable gain control - you always want to boost the signal only up to the level of intelligibility and no higher - anything else, and you amplify more noise than signal. That takes experience and a good ear to determine.
The 320 is superb for utilities. There are a great many voice stations still on the air, and the 320 will do the digital modes - those that can be decoded, anyway - very easily. I've been using the 320 for years, and had very little trouble with most of the modes (except HF FAX, and that's only because I haven't been able to properly calibrate the soundcard, it's so damn cheap...). Perhaps the big plus with the Satellit is that it doesn't need a PC to work, so it's liable to be inherently quieter than the 320. However, the edge in selectivity goes to the 320 very clearly, as is the ability to build nearly an unlimited number of files to fit whatever you want to try to hear.
Most all the RTTY news services are gone to satellite, contrary to what you might see and read in other publications. But there's still quite a lot to hear and see - if you want to get back into the Utility game, the Utility DXers Forum on Yahoo took the place of the WUN which closed down this past April.
And as for antennas - well, be a bit more specific. It sounds like you might be a cave dweller, but I could be way off base here.....73s Mike