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.