It really comes down to what you will use to drive the headphones.
If you're going to strictly use the Mackie mixer (or any other quality dedicated headphone amp) with these phones, then I'd go with the 250 ohm model.
If you should ever need to plug the phones straight into an audio interface, most can't provide a strong enough signal -- especially if they're bus-powered. In this case, the 80ohm model would be preferable.