The RS800 (clone of the GRE800) made a world of difference with my handheld.
If your system is an 800Mhz system that should be true because the antenna is tuned for that freq range.
The OP's system is in the 150-160Mhz range. An antenna tuned for 800 Mhz should be worse than stock in the 150-160 range.
They (RS) used to sell a much longer rubber duck antenna which would work better than standard rubber duck for VHF.
I use this antenna
Diamond RH77CA SRH77CA Antenna in the car on a suction cup mount inside the windshield
Valor BNCSCRS suction cup mount and it works both 800 and VHF quite well.
It's kind of long to use clipped to your belt but at least it's very flexible. (I recommend 2 right-angle BNC connectors between radio and antenna when walking around wit the radio to allow the connectors to swivel instead of applying forces to the connector on the radio.)