The "stub" antenna is the special antenna used when your at the race track. The smaller antenna limits the reception range, helping you listen to only the near vicinity. Remember the Sc230 is a "sport" scanner, designed for the Nascar race track. Do you live near what you want to scan? Up on a hill or in a valley? I'm gonna guess the factory duckie (the bigger one) is sufficient for most of what you want to listen to. If you are having troubles picking up some stations, or reception is scratchy, Radio Shack sells a Center-Loaded Telescoping Whip Antenna,
Center-Loaded Telescoping Whip Antenna - RadioShack.com that I use and it picks up alot better than the factory. Downside to it is it isn't flexible. acepilot340 posted what looks like a good flexible antenna at Scanner Master. You can always do better than the factory duckie antenna, but the question is do you need it.......