Indoor, outdoor, back of set, automobile? Easy answer is the one tuned to the frequency bands you like to monitor and mounted as high as possible away from sources of RF interference and obstructions.
I have an antenna on a pole about 10 feet above the top of my roof and it works great. My house has steel siding and regular antennas don't work as well. My handhelds I use a telescoping antenna when I'm hiking or at the park and it seems to work really well. I wish I understood the antenna tuning for best possible reception though.
Speaking of the TRX1, right next to the antenna, is that the led light that can be programmed into certain colors? I have tried everything on mine but it dont work. Is it something Im missing?