Both SeoSamba and WordPress Multisite have loads of features and extensions that can give you certain advantages and bring incredible benefits to your online presence. However, we are confident that SeoSamba is the best overall solution for a multi-site franchise network or a multi-location online store business model.
SeoSamba is going to be a better choice for several reasons - one of them is that SeoSamba is designed to meet the needs of franchise marketing companies, whereas WordPress Multisite is an afterthought, an additional layer on top of the existing WP framework due to popular demand.
WPMS is supposed to offer a reasonable way to tie together several existing WordPress platforms, at the same time SeoSamba is a real multi-sites platform that allows you to manage an unlimited number of websites.