The difference between these 2 plugin is very simple:
WP Blog and Widgets Pro : Create a BLOG PRO tab in WordPress menu tab where you can manage the the blog post. We have create this plugin because many users do not want to use WordPress POST section for blog and need a separate section for blog.
Blog Designer – Post and Widget Pro : This plugin work with WordPress post section and design the post.
I am very sorry i purchased this software. The documentation and support are very weak and so is the software?