That's a big question. Best is a relative term. Your team should sit down prioritize what you want from a BI tool. I've listed some considerations below. Incorporate that into a discussion about how it will be used and who will use it. Primary consideration should be whether your BI environment will be self-service or whether BI will be delivered to users. Some tools are easier to learn than others, and some vendors good with training and others are not. I would consider Tableau, PowerBI, Spotfire, and Qlik, but I am sure lots of folks have opinions on this. And of course, cost is going to be a factor.
Connectivity - what can the BI tool connect to
Speed & Volume - how fast does it load large data sets (this is HUGE)
Visualization Types - not all BI tools have all visualization types (ex. Spotfire doesn't have an out of the box area chart)
Functionality and Features - what can it do and what can it not do
Incorporation into your ecosystem - a lot of companies go with PowerBI because they already use MS products and it incorporates well with those
What do you have to purchase - how many products do you have to purchase to deliver BI to users in a way that makes sense for your company; make sure you understand what is "out of the box" and what is an add on purchase and the value those add ons do or do not give
