Jefe hands down.
I paddled a Nomad 8.1 for three years on various runs (including Vallecito, Baker's, Second Gorge Lime Creek, Rio Brazos) and always had fun, although a gallon of water sloshing around in the bottom of the boat was a nuisance.
This year I replaced the Nomad with a Jefe. After moving the seat forward, I like it a lot better than the Nomad. It is more comfortable, boofs better, is faster, rides higher, and is dry. I'm 5'10" and 170 pounds.
If these are your only two choices, then go with the Jefe. But the world is full of options.
Shawn Fullmer aka The Professor