how tall are you? how fast will you ride? how hard do you corner? how hilly is the route?
short arms favor shorter legs, high rpm spinning, cornering clearance, and less leverage.
longer, the opposite.
i have fairly short legs (29" inseam), ride 20mph +/- 5 in rolling hills, and watch my corners. i started with 165 and moved to 170. i like the extra leverage, upped my gear one tooth to slow the spin and take advantage. have yet to strike a pedal, but do try to keep the bike more upright in the corners.
$0.02.