Team Site Provisioning

Luke, we find ourselves in the same position.  Our Sharepoint deployment has been on hold for a year now as we continue to sort out details and inconsistencies with modern sites, groups, teams, etc.  We do not want to waste time building on the old platform, yet the modern UI and 365 apps are not ready for enterprise.  Yes, you can link a Team to a group, but there are several bugs, including issues with integrating planners, document view, sharepoint URL link, and email link.  This is just one of many odd administrative issues that get slow attention after the products are released.  For instance, until a week ago, it was not possible to recover a deleted 365 group, which caused all sorts of headaches mentioned on the community.  Granted this is a much appreciated feature that has been added now, but it probably should have been included in the public release if "groups" was intended for businesses, let alone enterprises.   

Improvements are coming, but from an admin and functionality side they are slow.    If your organization is small and you are willing to relinquish some administrative control and let the environment be "organic", I would probably recommend groups as this seems to be the way of the future and will keep you from rebuilding in the future.  That being said, even if you build on the groups platform, you may end up having to rebuild/move things around as microsoft continues to figure out what the product is going to be.  If you are an enterprise or want administrative functions, I wouldn't trust groups just yet.