1) GoAutoDial has a prettier interface (admittedly this interface can be transplanted into Vicibox if the version matches). GoAutoDial is also CentOS (which makes a difference to some enterprises which require Redhat Linux or a relative of same, which CentOS is).
2) GoAutoDial is supported by Gardo (and I think he may have another technician now as well, but I'm not sure) whereas Vicibox is supported by The Vicidial Group and pretty much "anyone" who knows Vicidial (which is the actual software being installed). Of course, I support both but I'm an independent, nosy person I may not count.
3) Vicibox WILL install (out of the box, as it were) both the SVN (latest code, 2.4 developer trunk) and even Cluster versions (ie: a box JUST for web or JUST for dialer or several for each purpose or the SQL or ALL or any mixture). Whereas GoAutoDial is predominantly designed for single server installations. Ordinarily Single Server is about 25 agents max unless the hardware is extreme or there are no recordings or compression at all. If any of those things happen, you may not even get 25 agents on one box.
4) Vicibox's release dates seem to be more recent, last one about a month or two aga (although we haven't had one in a while since 3.1.9, but that would likely be because the bugs seem to have worked out and Kumba is letting it wait until 2.4 releases, as a guess). GoAutoDial has been a few months since release and historically is about once every year or two.
5) Vicidial IS a GUI for asterisk. That's kinda what it does.