1. Features- eg. speed of survey creation, speed of obtaining information, matrix questions, filters, logic
2. Reports format - real-time reports
3. Convenience - eg. online access, no software, friendly interface, advanced response collection (email, web, popup, web widget)
4. Support - pofessional and very helpful customer support.
Mysurveylab.com we use for product testing; FUTs, opinion survey, satisfaction survey.
Main benefits: speed of obtaining information, speed of survey creation, ease of use, reports, online access, no software to install or download (all you need is web browser), secure due to HTTPS/SSL encryption.
I strongly recommend mySurveyLab.com!