Wish I had seen this when it was 'fresh'!
If there's a particular band you listen to more than others, select an antenna optimized for that band. If you want to listen to everything, optimize the antenna for the lowest band, as in as long as possible, within reason.
In most cases, the antenna in/on the car radio will work just fine. As long as the antenna is outside of the car's metal body, it will work 'better' than if it's inside.
Acanners are receivers. Receivers just are not as 'picky' as transmitters. In most cases, more is better. And the only place you will be able to tell a -huge- difference is in your wallet. Unfortunately, that difference only increases in 'negativity'.
- 'Doc