The Roman Riddle

Julius "Full-Haired" Caesar is directing a legion of troops (6,000 men) towards Gaul. He has two options:

OPTION 1: Schliffen-Style Manoeuvres

If he goes around the armies of the barbarians, he will be hit by guerrilla attacks that slash 10% of his forces. In the process he will capture undefended towns, and then destroy the barbarians at a battle that will lose him 60% of his remaining forces.

OPTION 2: First Strike

If Caesar does a head-on assault, he will suffer 70% casualties, but not be (literally) decimated by the guerrillas.

Which way conserves more of his forces?