I think Luigi doesn't have a central scheduler which allows you to run tasks hourly/daily. In the docs it suggests that you can use cron to trigger tasks periodically. This was the major reason why we didn't pick Luigi. Airflow provides that capability and also has a nice UI where you can manage the DAGs (visualize the task instances, set task states, etc). It's a young project and the codebase is clean and easy to understand. Airbnb is also actively developing on it as far as I know.
Airflow by airbnb is a nice alternative to luigi. We've been using it for our ETL and it's been working greatly so far. http://airbnb.io/projects/airflow/