Wordpress remains to be a better option for me on comparing nucleus. I've been preferring Wordpress for most of my blogs and found to be flexible in customizing the most common features of every bloggers/webmasters do. Like HTML code, plugins (can find several plugin's for WP CMS), certainly the pre-designed templates (an easier choice for every blogger, and it just requires a little modifications in it, not as a whole), inclusion of widgets, etc. Guess certain features that are wanted for designing the blog are not available/complicated in finding it in the other CMS - Nucleus.
However, it depends on you in preferring the either one. Look in for the features, upgrades of the platforms and stick to the perfect one that helps your website grow even better.