Having a robust A/B, MVT testing infrastructure that lets you test on page components is the most important thing but it is only a small part of the equation. I don't have a comparison chart of Optimizely vs T&T features but there are some common feature sets and every provider lacks one or the other. Having used Optimizely, i would say Optimizely has about 30-40% of features that other enterprise level products have (personal guess not based on metrics/facts!). Some areas where the smaller products lack features are

- Personalization, segmentation and targeting (I am not talking about basic geo-targeting, repeat users, technographics etc). The features in this category can go way deep.

- Industry specific features (Having a one product fits all approach will be hard to sell in many industries. Eg: There is a huge difference in how retail and publishing uses a testing product)

- Reports and analytics (every product provides charts and graphs but this is one area where you can keep building and you will still be lacking some thing or the other)

- Upsell features (recommendation engines, mobile, social)

Many of these additional features are hard/time consuming to build and will not make sense for a good percentage of users but having those will help the product to score in the enterprise land. After a certain point when you have all the basic features, identifying what to build is probably one of the hardest tasks.

Obviously features are important but it turns out that most businesses simply want an easy to use platform that "just works." Most of the customers who switch from T&T to Optimizely start off by trying both concurrently and evaluating whether Optimizely has what it takes to supplant T&T. When their T&T contract comes up for renewal, they shift their entire budget to Optimizely.