Quadcopter RX TX questions
It's better to go with something that you're allowed to use. That depends on your region. A shortlist follows (source):


USA/Canada: 72 or 2400MHz.
Europe: 27, 35, 40 or 2400MHz.
UK: 459MHz.
Singapore: 72 or 2400MHz.
China: 1400, 2400 or 5800MHz.
Australia: 27, 29, 36 or 2400MHz.
New Zealand: 27, 29, 35, 36, 40, 72 or 2400MHz.


Even within these bands there are often restrictions, so best to check. You also want to make sure you're doing something to both tolerate interference and not cause undue interference.

After all that is said and done, then you can worry about which is better. Roughly speaking, lower frequencies carry further but need a bigger antenna. Higher frequencies attenuate more but can have a higher data rate. You have to make a trade-off.