Hi Drover, you are right about 2.4 not being as prone to 'bleed over' from other frequencies. In my opinion it's the way to go.
Next, although you may only have 2 models now you may find that there is a chance that could expand and for that reason I would add to what others have said and go for computerised kit. There are a few great 2.4 radios out there and with some good functions all for not too much expense.
With a computer radio you can reverse the direction a servo turns without having to take it out and adjust pushrods. You can choose how much it turns (from zero to 120%) and lots lots more just with the press of a few buttons. No more buzzing servos when the pushrods bottom out.
If you want to turn something like a gun turret then it may be an idea to look for a radio with one or more rotating switches (I think they are called 'pots' short for potentiometers but don't quote me) or with some radios you can get slider switches.
My radio is used for flying (or was) and I now sail my boats with it. Each model has a name and when I turn my radio on I just find the model name and all the settings are remembered. This goes for all the new computer radios and it's a great system.
So in brief...... 2.4ghz computer with model memory and a couple of switches and/or dials.
Once you have it if you can't understand some of the complicated jargon (like this post
just come on here and someone will be only too happy to help....... Let us know how you get on and what you choose. U2