I was tasked with rolling out a "self-service" BI/reporting tool for all of our internal users a while ago. My company is on AWS, and at the time QuickSight was just getting ready to begin the preview period. We felt QuickSight would be a good option since our data was already in RDS and we had just decided to buy a Redshift cluster as well.
I evaluated trial versions of the following tools: Looker, Periscope, Mode, Tableau, QuickSight, and Microsoft PowerBI. They are all very similar in my opinion and at the end of the day will all provide the ability to view dashboards and reports through a web interface. The tangible differences come down to how exactly data refresh happens and the customizability of dashboards and reports. Each tool also offers varying degrees of useful edge features like sharing, alerting, privileges, and saved queries. I eventually settled on Microsoft PowerBI.
The biggest advantage for using PowerBI in my mind is the degree to which reports can be customized. Compared to QuickSight, PowerBI is leagues ahead in terms of customization, while still providing enough predefined templates that you are not constantly thinking about trivial styling choices. More than any other feature, Microsoft gets this right and executes on it better than any other BI tool I've tested. There is even a growing gallery of community visualizations that can be used for free (https://app.powerbi.com/visuals/), and you can write your own visualization templates using TypeScript.
I've been using PowerBI for several months now, and each month Microsoft releases an update that targets the biggest frustrations I've had, such as lack of pre-defined data connections or pre-defined styles. It's still missing some key features I would like (different forms of aggregations, etc) but it's still better than QuickSight, no question. As far as pricing goes PowerBI actually starts with a gratuitous free tier. The free part ends when you want to enable the "groups" feature, which allows you to set up privileges for which users can view certain dashboards. The paid version also allows more data to be stored in the SaaS. You need a premium account which is $10/per user/per month. The pricing + the speed of creating and uploading reports made PowerBI the winning tool. So far the team has been very happy with it.