Taking the voucher assumes you will be traveling again and thus spending more of your money at some point in the future. Why not take the $100 off, earn miles on the flight (any flight) you were going to purchase anyway? Miles are earned on the flight you purchased with the voucher which increases its value relative to the miles.
True the voucher can't be combined but for an infrequent flyer the ability to amass the correct number of miles for an award (a somewhat imprecise target) may take a while which reduces the miles value. The miles also impose an additional cost on the passenger because the booking process is more complex and thus requires more time.
I suppose it is not cut and dry for everyone but if I am offered a voucher or miles I will take the voucher 100% of the time without a second thought.
Good points.
If someone has concrete plans to purchase additional travel and can use the voucher promptly, then the voucher is better than miles that will just grow moldy.
95% of my travel is business-related and, while I am sure my clients would appreciate the gesture, vouchers are of little value to me.
I have used them for overhead, non-billable travel, but I try to minimize that sort of travel.
It is good that the OP had an immediate need for the voucher... before additional restrictions get imposed on them.
"DL is announcing today that travel vouchers are now only applicable to M fares or above, for travel on Tuesdays in months with 31 days. It had come to our attention that some persons were gaming the system by using the vouchers for their original intended purpose, forcing us to implement controls to prevent this. It was hard decision to make, but it was the correct decision."
