There will be serious dissension regarding your question but I still use $.02 per mile as a guideline. Subtract a percentage if you will for the reduction in amenities in both FC and Coach,
I use most of my miles for Int'l BE fares so if the fare is over $1,600 RT...knowing I can use a PMU for an upgrade...I'd go with the 80,000 miles and choose an award certificate.
Most Int'l B/E fares are considerably higher than $1,600 so if you can score an award seat for "only" 80,000 miles, I'd say go for it. I'll actually burn miles for an award certificate at around a fare of $1,000.You didn't indicate what class of service you were looking for or how many miles you were willing to spend.
I've fortunately got more miles than I can use in two lifetimes so I'm not as sensitive to the actual value of miles.