One benefit of in-person research is that the environment of the user can observed, which is more difficult to understand fully even if the user sets up multiple web cams in order to view remotely there is still a lot lost in translation. Another benefit is often the cost associated with in-person because the equipment is already available rather than with remote where the remote research costs include remote research equipment and tools. Remote research would still require research, testing the design, recruiting users, compensations and analysis so in-person can often be less costly.
Quantitative usability testing focuses on actually numerical data in order to provide repeatable results among the specific user groups. It’s the more scientific approach in research, which gives a formal means of design testing as well as analysis. With quantitative there will need to be a much greater number of participants in order to gather information that crosses a spectrum of individuals with different skills and knowledge of similar sites. With a larger number of varied participants and all the right questions to gather the data, the results will offer more of a generalized overview of users which in turn can mean that the product or site will reach more users and maybe different user groups than would have been initially expected thus adding more insight to the product or site.