This question is a tricky one to answer; if you provide more details of how many towers are in your area, how far you are located from your preferred tower and your location environment and the surrounding area, i.e. if it is built up or not it might be easier to answer your question.
I would however suggest to stay away from the antenna's provided by iBurst itself; as they are more expensive and do not work as well in all scenarios as some others do.
There is one other flat panel that works exceptionally well - a member of the forum designed it - if I recall correctly his name is GRES (search iBurst posts by his name).
It is however very directional and I would not recommend it for outdoor use as the slightest movement will affect your connectivity, (unless you remove the two copper rings on the backplate, then it becomes far less directional and still functions as expected) however it cannot be used in an environment were any other metal objects are located.
I am currently using it stuck against a window with self adhesive Velcro, it works better than any other flat panel I’ve tried. It functions best at a range of < 1.5 Km’s. I purchased one from http://www.phoenixnet.co.za.