Answer
The path with the larger radius corresponds to the more massive particle.
Work Step by Step
The force on the particle due to the magnetic field provides the centripetal force to keep the particle moving in a circle.
We can find an expression for the radius of motion:
$F_B = qvB = \frac{mv^2}{r}$
$r = \frac{mv}{qB}$
If we assume that the two particles have the same speed, the more massive particle has a larger radius of motion.
The path with the larger radius corresponds to the more massive particle.
