Hello joey,as explained above by MrStrang, i would opt for the radio he mentioned in his post as "cheaper in the long run". I looked it up, and if you can stretch your budget to get that Futaba radio, then it will serve you for many many years to come. There may seem to be many things about it that at this stage you don't have a clue about, but hey, you will be growing with the use of this radio, so as time goes by , and asking lots of questions about the extra features , you will find as your fleet of aircraft grows and your knowledge of all things pertaining to the wonderful hobby of our's grows then you will start to get the benefit of having a good radio from the beginning.
Your trainer aircraft will only require the 4 basic channels now, but later you may well be looking at a model with flaps , retractable undercarriage, so there alone is the use of 2 of the extra channels you will already have available to you, without the added expense of buying another radio 18months down the track. Also is the feature of having to be able to programme in more aircraft to this radio, so as you choose what model you are going to fly from your fleet, then all the trims for that model are already set in the transmitter . Saves a lot of trim flights later on. So hope this will help you in you decision, and if you have further questions , there will always be someone here to help you . All the best in your venture into this wonderful hobby of ours.
Bill