I guess the main difference is that the graphic and writing styles are more scattershot: the pictures are lifted from a variety of sources, and the text is by several authors, not necessarily coordinated or edited much. Some of the charm of the original SotSF
is lost with this, as the older work felt more "authoritative" somehow for its integrated looks.
Of course, these newer versions also concentrate on onscreen starships, as there are so many of those nowadays; the reader may be more inclined to disagree on some of the interpretations, having formed his or her impressions on particular ships already. And it's statistics from that point on, as everybody will find something to disagree with in the plethora of articles, while Guenther's work had just three or four "canon" ships and mostly non-controversial original art for the rest.
Personally, I lament for example the lack of detail in describing the onscreen variants of the Ambassador
class model. The text mentions the differences, but the artwork does not follow...