Basically sword offers potentially better 100-0 chances. An 8 hit flurry is hard to beat. But I actually like polearm more than sword for killing stsf.

Most stsf warriors, especially strong ones, are running their wimpy pretty generous specifically to avoid dying to large burst. Unless the stsf warrior has lagged himself, he's probably wimpying out of your flurry. Now granted you can pretty easily wait for him to lag himself to drop the flurry but that's still dependent on him.

On the other hand cutoff gives you a counter to wimpy. Not a great one, granted, but we've all had those fights where we get cutoff 3-4 times in a row. And usually a suited up giant warrior only needs one or two chops to kill elf warrior by the time elf warrior tries to flee.

Also polearm is just super hard to riposte. It's not just the less attacks, it's the nature of the weapon spec. Pole and spear/staff are super hard to riposte. I would take sword over pole for fighting most people but specifically for elf stsf I'm taking pole.

And finally, one of the best ways to win a pk is strong progs because the enemy can't factor it into the game plan. There's inherent strength in good random progs. You have to be quick and a good pker to maximize the effectiveness of the prog(timing your skills to optimize their effectiveness, adjusting your next command based on what just happened etc) but if you are then I don't think you should discredit them. Pincer staff isn't exactly hard to get, neither is thunderlance if you're goodie. I can also think of one or two more area explore/questy polearms with solid progs.

There are few things scarier for stsf I think than an enlarged chopping giant with 70+ damroll and a prog happy pincer staff.

If stsf elf is reticent to burn aura/shield for 1v1s (which they typically are), that's flirting with death every time.

In summary pole might take a bit more skill and game knowledge than sword, and it might lack the wow factor of a flurry, but I'm choosing it if I'm specifically trying to kill elf stsf. Flurries might "win" more fights (make them flee) but I think pole gets you more kills against stsf and also gives you some extra survivability.