I always look at decisions like this based on what I have the most of. I don't have $1,400 or $2,800 to spend on getting my butt in a nice leather seat. I have hundreds of thousands of miles collecting dust.

For me it's an easy decision, use the miles. I don't care what it costs per mile or any of those other calculations, I have a ton of miles. I don't have a ton of cash.