A year in industry would probably be more beneficial - You'll simply have more experience. I've not heard of places giving major responsibilities to summer candidates simply because there isn't enough time to follow it through to the end. A year in industry would still give you a lot more experience and things to work on.
The company may also offer you a job, which is something not typically handed out to summer placement staff.
My university reckons doing a year in industry will, on average, give you the skills to improve your overall degree classification by an entire grade. You could still do some study while working (preparing for final year modules) and perhaps carry on your project as a final year project with the university - The company may support you for this.