Originally Posted by
NOLAnwGOLD
So the GUCs are best value IF you can use them. If you fly AF most, be really careful of the terms of use (best to by DL marketed flight on AF/KLM and if you plan significantly ahead, you can often confirm them at booking). In fact it's just best to use them at the time of booking (via an agent on the phone).
For me, I usually do the $200 vouchers since they book as cash and count towards MQDs. But since you aren't US based, MQDs don't count so the miles might be best value as noted above.
IIRC on AF GUCs only upgrade the TATL segments, not flights beyond CDG (plus, of course, any DL or DeltaConnection operated domestic and transborder connecting flights with FC).