Obviously, I'm biased as to which is the best book! If you want unbiased opinions about both Stencyl books, then I recommend reading the reviews on Amazon.com
Also, if you go to
www.packtpub.com and search for 'Stencyl', you can read the first chapter of each book by clicking on the 'Free Sample' link. When in the free-sample section, the books are referred to as 'courses', but they contain the book content.
Also, if you visit my web site,
www.stencylbook.com, you can download a complete free chapter - it's a 'technical' chapter (rather than the book introduction) so you'll get a good idea of the style and depth of information.
As I understand it, today (Monday 9th Jan 2017) is the last day that Packt are offering all books for US$5 each, so you could bag both books for US$10.