It is a mater of taste and requirements. Although I still use Iron Router (for historical reasons), my advice is to not use it, cause it is an overly complex package with pending issues. Alternatives are: 1. no router 2. flow-router.
Almost every bit of Meteor code I’ve seen in the wild uses iron-router. It’s even recommended in the Discover Meteor book. If you’re used to routing a-la Rails, then it’s highly recommended because you will feel at home and waste less time.