The longer antenna should perform better, especially on frequencies near 150Mhz where the gain is focused (as the manufacturer is aiming to sell to the ham radio market). Assuming the length doesn't make the handheld too clumsy for your setup, I would buy the longer one as the price is also quite attractive. A circumstance where it may be of benefit is when a specific police vehicle is transmitting simplex (not through a repeater station). The base station dispatcher would be easy to hear due to its antenna height and wattage, but a responding car could be in a location where its signal is heavily attenuated.

Performance in the aviation band will probably be better on paper, but I doubt it would be noticeable. Transmitters for aviation work are going to be fairly high powered, and will use antennas that have pretty decent line of sight clearances. With your short distance to the airport, the Uniden's supplied antenna will pick up fine. Plus aviation broadcasts on A.M., which doesn't have the capture effect problems a F.M. signal might have. A weak A.M. signal can possibly be heard faintly. With F.M. the signal is either captured by the receiver, or lost underneath the noise floor (no middle ground).