Dual channel (not dual band, dual band would be like the 888K that uses VHF and UHF) is actually really not all that awesome with single transceiver radios at big games.
There are too many people that talk too much when they don't need to at the lower levels so that ties up your radio. You could end up listening to a 2 min long transmission of somebody's hot mic and miss out on all the good info being passed on the other channel.
If you hit your PTT at the wrong time you can end up on the wrong channel and not know, or you could be spending some fiddling with your radio every time you need to swap transmitting channels.
So its really only useful at the upper end of the command chain where there are less people on the nets.
At smaller games its cool, but often not needed since you can fit the whole team on one channel anyways.
Dual radio/PTT setup is the way to go for this function (aka more money!
)
As for spying on comms, its not unheard of, usually does not happen, but even when it does its pretty hard to detect. This is what code words and nicknames are for, determine them before games and use them always.
There is also the option of switching to digital as well, but again, money.