A discone is intended to cover a very wide spectrum of VHF/UHF/SHF frequencies for wide band scanners. It's bulky in comparison to a simple whip and won't necessarily perform any better. A dual-band VHF/UHF Amateur antenna (2m/70cm) is pretty good on both VHF and UHF airbands.
It really depends on what you want to listen to and what receiving equipment you have. If your interest is primarily airband, then my recommendation is still good.