Furlough you forfeit your Redundancy Payout to retain service benefits and remain an employee on the Seniority list while effectively on LWOP. Your pay step is frozen while on Furlough but service benefits continue to accrue.
Redundancy you get paid out and your Seniority number is reserved. When/If re-employed all service benefits are reset and you're effectively a new hire Pilot.
Regardless of which option a Pilot chooses, it's last off first on so assuming all Pilots are re-hired, no one gains or loses Seniority by choosing one over the other.
Furlough cannot be forced by the Company. Once redundancy notices have been issued each Pilot will be given the choice.
A Pilot who chooses Furlough however, has 3 years to change their mind and take the Redundancy Payout so the Company must account for the debt,
The numbers are not finalized and nothing has been ratified yet.