We cannot go into the details of a comparison between XOOPS and Post-Nuke, as this would be rather off-topic here. For a discussion of XOOPS vs. Post-Nuke, see XOOPS vs. Post-Nuke. There, among lists of pros and contras, you will read this:
I'm an architect. My teacher always told me that there are no "bad tools". There are only "bad craftsmen".
Find your own way to work - it's not a race, not a competition, you don't need to have the better machine to win. The best sites won't flash with decorations, tons of blocks and gifs. They are
made with the same basic tools, CLEAR AND WISE IDEA, and lots of custom made details.
Innovate - not imitate. 
