1) The distillation of a single metric, Visibility Score, across a basket of keywords, for both desktop and mobile search, trended over time for your domain. It helps SEOs avoid overwhelm with all the different ranking measurements it's possible to track.
2) The logic that joins Google Analytics with Google Webmasters (Search Console) data to provide a good-as-it-gets overview of search rankings' contribution to traffic.
3) The research tools and 'Opportunity Score' metric to help prioritise which keywords to aim for.
4) The speed at which the company is innovating and adding new features, and responding to changes in the industry and the way Google provides its data
5) The customer support and responsiveness to needs. First class onboarding by phone and ever-present help over Intercom.
Definitely do the free trial. If you look at the service tiers and don't find one that suits your requirements, speak to the company and tell them what you need. I have found they are willing to customise a package for the customer which then appears in the upgrade options for you.