To your question about Unbounce vs Optimizely, Elise is right: They are not really comparable.
We use both. A simple way to split the two is to use Unbounce for your landing pages for paid ads where you have a single-minded conversion in mind and don't want to offer any distractions like site links, menus, social share buttons, blog subscriptions.
Optimizely, as Elise said is for your main site pages. Clearly you may still have a conversion intent on your site pages, but when visitors come for free (search, referral, social) you can afford to be a little more generous in terms of the click paths you allow. When you pay for the visitor (ads), you can't.
Also, with visitors from an ad you know a lot more about their intent because they have used a search phrase, and seen your ad then clicked it. so you can afford to offer a very narrow option (usually one) whereas your main site pages may need to appeal to a wider variety of paths and interests, and hence click paths you offer.
Having said that, think about the pages that you would use Optimzely on. It is likely to be your busiest pages where you may have a single-minded conversion intent. We use Optimizely mainly to test the affect of stripping out options (footers, social shares etc) and usually find that less is more, or of the location of forms. With that confidence we then permanently strip out those options / make other changes from our busiest pages for which there is a single-minded conversion goal (subscribe, buy, contact, book a meeting etc.).