As far as I can see you just need to look at potential teams with and without these players.
Team if you Re-sign Matthew Head:
1. Benji Marshall, 2. Peni Tagive, 3. Dean Collis, 4. Chris Lawrence, 5. Shannon McDonnell, 6. Tim Moltzon, 7. Matthew Head, 8. Todd Payton, 9. Robbie Farah, 10. Bryce Gibbs, 11. Gareth Ellis, 12. Chris Heighnington, 13. Liam Fulton
RES: 14. Keith Galloway, 15. Bronson Harrison, 16. Dene Halatau, 17. Taniella Tuaiki
Team if you re-sign Ben Te'o
1. Shannon McDonnell, 2. Peni Tagive, 3. Dean Collis, 4. Chris Lawrence, 5. Taniella Tuaiki, 6. Benji Marshall, 7. John Morris (You know it'll happen), 8. Todd Payton, 9. Robbie Farah, 10. Bryce Gibbs, 11. Gareth Ellis, 12. Chris Heighnington, 13. Liam Fulton
RES: 14. Keith Galloway, 15. Bronson Harrison, 16. Ben Te'o, 17. Dene Halatau
While the pack looks a lot better in the second team...you still have Morris at half. IMO if Tim Moltzon was half it'd be better...but still.
IMO Matt Head must be re-signed.