I hear that 1 1/8 threaded exists. It might be really hard to find headsets and stems though. And since you axed:

Benefits of threadless:

Stiffer
Stronger
Lighter
Cheaper
More selection of stem angles and lengths
Simpler bar swaps if you can find a poptop stem
Doesn't channel water and sweat directly into your steerer tube like threaded does; keeps water and sweat out instead
Quicker, simpler headset adjustment (needs just an allen key)

Benefits of threaded:

Easy to jack the stem up and down
Looks retro

Did I miss anything?