In theory the 75Mhz channel (or any higher frequency channels) gets better reception due to less attenuation in air with higher energy waves.
But you see, the 25Mhz band only has a few channels whereas the 75Mhz band has quite a bit more. So your interference with another dude's radio who is on a channel close to yours might be worse.
But the 2nd part is only speculation so I went with a 75Mhz.