What VWO has that Optimizely doesn't
- VWO has (JavaScript based) A/B and multivariate testing and split URL (based on traffic redirect) on while Optimizely is strictly (JavaScript based) A/B testing. You cannot do multivariate testing with it.
- VWO has heatmap and clickmap reports while Optimizely doesn't
- VWO has various advanced features such as visitor segmentation, cross-domain tracking, testing behind login wall pages, test results notifications, variation screen shot generation, etc.
- VWO has team collaboration such as multiple-permission based logins and subaccounts. Optimizely doesn't have that.
- In VWO, for all plans, CEO equally shares the support work ;)
What Optimizely has that VWO doesn't
- Changing layout of the page. Optimizely has a drag and drop feature in its test designer which is useful if you want to test different layouts (say sidebar to the right). To achieve the same in VWO, you need to enter some CSS (say float:right v/s float:left) as there is no drag-drop support (yet)
- Since Optimizely exclusively focuses on A/B testing (and not MVT), in its test designer you can change several elements of the page (say headline, image and text) at once to create a variation. In VWO (currently), you need to change one element at once for A/B test and multiple elements for multivariate test.
- In optimizely, results update on the page in real time. In VWO, results are also realtime but you have to refresh the report to see latest results (no auto-refreshing)
I hope this was a fair comparision. I wish Optimizely team great luck for their product. I hope A/B testing market is big enough for multiple players to survive!