Aside from the religious wars regarding which platform is best, and whether or not WordPress is easy to learn..... the answer to your main question about Google optimization is that "it doesn't really matter" whether you use Wix, Weebly or WordPress. All of those platforms have the same ability to be optimized in search engines. You have full control over the Meta tags, body copy, link structures, etc. These are all the things you need to finesse in order to make your site as "search engine friendly" as possible. Wix, Weebly and WP provide equal control over all those components of your site. We've developed sites under all three platforms at my website development company, Sync Interactive, and have had great success promoting all of them in the engines. So from an SEO perspective, like I said, it doesn't really matter which you choose.
Remember, however, that optimizing your own site is only a fraction of the battle towards getting your site to the the top of engines. You also need to actively promote your site on the internet by participating in other blogs, forums (such as this), business directories, social channels (facebook, twitter, linkedin, etc), online news coverage, and anywhere else you can get high quality links pointing to your site. And this, again, has nothing to do with Wix/Weebly/WordPress.
Choose the platform that's most comfortable to you, and most suitable to your needs. Do you need to do a lot of blogging with rich blogging features? Then WordPress is the way to go. Do you need a more flat, static website with just a little blogging? Then Weebly and Wix will serve you well.
