AR7 are a camber park ski. They are one of Armada's stiffer skis, but still aren't too stiff compared to some Volkl Walls persay, or even Suspects. They can go all mountain better than most of the other park skis, but won't do well in pow. They are probably the best all around park ski of the 3, if you are a slopestyle type of skier.
T-Halls are more buttery than AR7s, much softer in the tip and tail, while keeping with the camber profile. They are a highly praised raIl ski, and hold their own on jumps, especially if you aren't very big. They won't be as good out of the park as the AR7, since they are a softer ski and will probably chatter some at higher speeds.
Halo's are the most unique of the three. They have elf shoe technology, a 5 dimensional shape, and are rockered, unlike the other 2. They have a very tight turn radius and can be taken out of the park, even into pow. They are very buttery and playful, and a lot of fun.
All of your options come with the AR50 sidewall so they will be quite light, and will all be some of the most durable skis on the market. Hope this helps.