I think as per the earlier market research on the predictive dialer, the actual gain was comparatively small. But today many market research campaigns are little different from telemarketing campaigns in overall talks. The live call rates and wrap times are quite low, as calls divert to voicemail.
Companies who are using hosted predictive dialers are on predictive gain over progressive calling. Predictive dialer uses algorithms to minimize the time that agents spend and dial multiple numbers at the same time. They have the ability to make use of call metrics to predicts whenever the agent is available for next call. So, they are doing quite well in the market with their distinguishing feature.