Will you be using them in Tower, Approach, Area or all three? There are a few providers now including Selex, Frequentis, Nav Canada, Saab and Park Air Systems. For a radar environment Selex's SATCAS 2000 enables interaction through the data labels on the Radar screen so you can keep an eye on what is going on, or you can have electronic strips on the same screen with a smaller radar picture. Park Air uses electronic strips on a Wacom panel but there is no interaction through the radar screen which means you spend more time looking at your board while inputting data/instructions. I have no experience of the other systems, as for which is the best that depends on what you're looking for in the system. I will say this though, SATCAS, Frequentis' smartstrips, NavCanada and Saab are proven systems in a live approach/en-route environment as opposed to Park Air's which as far as I know is only in live use in the tower environment with Jersey being the guinea-pig for the approach versions later in the year.