Use a transistor by all means, a low/highside drive would be better. You want a fast level change.
Don't forget that low on resistance only occurs when the device is fully driven. Switching provides a lot of time for when the device is not fully driven (rise & fall time) so a large potential for over heating.
If you can get the specs for the motor it will make choosing a FET easier, however, although robust when properly specified, they are easy to pop. So always over-specify (they are so cheap!) (I buy them by the tube) and use a heat sink. Try running for a moment and see if you notice a temperature rise.
Don't forget a (fast) fly-back diode!
And once again, read the specs and the manufacturers recommendations.