When comparing Instapage vs Wordpress.com, the Slant community recommends Instapage for most people. In the question“What are the best website builders that don't require coding?” Instapage is ranked 8th while Wordpress.com is ranked 9th. The most important reason people chose Instapage is:
The auto-mobile feature means that any page you build, will automatically be viewable on any mobile device automatically.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Mobile-friendly
The auto-mobile feature means that any page you build, will automatically be viewable on any mobile device automatically.

Pro Easy to get started
There are three easy ways to get started. You can use the drag and drop editor to build your own page from scratch or customize a template. You can also import current web pages and edit them in the drag and drop builder.

Pro 100+ templates
There are over 100 ready to go templates for lead generation, webinar registration, mobile apps, and thank you pages. There are new templates constantly added as well.

Pro Built-in tools for A/B testing
Pro Huge collection of free and paid themes out of the box
Pro Pretty easy to create and maintain a blog
Pro Import from other blogging platforms
Such as blogger.
Pro Bulk media options
Pro Widget management
Pro Support sort post by name
Pro Powerful analytics out of the box
Pro Plugins for every occassion
There are a wealth of plugins that can cater for just about every requirement you may have, and many of these plugins are free.
Cons
Con Web-based, not a proper application
Con Limited to landing pages
Instapage focuses on creating simple, static lead generation and click through landing pages.
Con Post must has category else it will be labeled as uncategorized
Con Freemium
Plugin cannot be used, custom html/css, Date Permalink cannot changed on free wordpress
Con Slow Speed
Navigating between action took around 3-5 seconds and longer for bulk action.
Con You have to pay even for custom css
