Which of these is better way to make money in long run?

A couple of months ago decided to get serious about IM, enough to make a living, not some get rich quick system. My goal is $5000 or more per month after two years. I am doing a lot of planning before I go ahead and launch anything. I have professional background in computer technology and writing about tech products so first thought the best methods was content marketing and monetizing with Amazon affiliate links, maybe a little adsense but I hear it is dying out somewhat.

I have done my keyword research, registered two domains in computer niches, one for tablets and one notebooks. I know how to write high-quality content and was going to launch the tablet pc site first and try to become an "authority" site of sorts on this subject even though I know it is very competitive. I figured if moderately successful I could launch another tech site (PC gaming, notebooks, etc.) every 6 months or so until I had a group of them.

However while planning this site I really have become interested in writing kindle ebooks. I was thinking of starting in a specific niche, either tech or motivational or some other niche, writing about one quality ebook a month, and build a blog around all my books or certain niches and refer back to Amazon. Seems like people are having success with this. I also have a really good domain name that would make a great title for a series of success related ebooks

I only want to focus my efforts on one of these methods my first year, really put my all into it. I know this may be hard to predict but which one has the best long-term potential - Amazon affiliate program or Amazon direct publishing?

Thank you in advance.