Hi Chev and all,
You ask which is better, then give one choice.
What's the difference between a duck?
One leg is each the same.
Your term "trunked" is ambiguous since trunking is used on UHF and 800MHz and you make no mention of either band.
OK, the center loaded antenna works like that strange duck, it's a center loaded quarter wave on VHF Lo Band, below the coil a quarter wave on Hi Band and a 3/4 wave on UHF. On these bands the coil is an RF choke electrically cutting off the top of the antenna. It's impossible to adjust to any resonant length on 800MHz which would be 9" below the coil or 3/4 wave.
OK, if you understand the tech talk you now have enough information to make a choice between it and the phantom antenna you never mentioned. OK, I'll take a shot in the dark and assume the phantom is the telescopic whip that came with the scanner. Unless you monitor Lo Band (you don't mention it so I'll assume you don't) the center load will buy you no advantage since with that exception it is electrically identical.