Well, I live in Arizona and hike here a lot. Mostly I use trail running shoes but also, occasionally, sandals. If you are coming to Arizona in the summer, I doubt that you will be desert hiking unless you like triple digit temps and blazing sun. Thus, you will be above the zone where cholla cactus are a major issue. Even with cholla around, trail runners are a good choice; you just have to watch where you put your feet, a good idea anyway.
Trail runners are comfortable, cool(ish) and light. Army boots are designed for the Army, not for the recreational hiker. They require break-in, they are heavy, hot and are not particularly well ventilated. I haven't hiked in Army boots since I left the Army and haven't missed them at all.
Pika is one of the most experienced desert hikers on the forum and he has been doing it for many years. If he says trail runners or sandals will work, then they will.
However, I disagree with his assessment of the modern combat boot. I have over 2,500 miles on
this boot and they show little sign of wear. I do keep the soles covered with Gorilla tape so they don't wear at all. They are comfortable right out of the box and don't require any breaking in at all. They are made of a leather that feels like suede. They have inserts in the leather for ventilation. They are cool in hot weather and warm in cold weather. They are the top choice for soldiers going to Afghanistan who don't use the issue boots.
This weekend, I hiked 10 miles in a pair of Keen hiking shoes and I hated them. Pine needles and little rocks kept finding their way in the top. They didn't have enough forward motion control on the downhill sections and I ended up with a hot spot on a heel. My toes are a tiny bit sore today like they would have also had hot spots or blisters after more miles. I NEVER get anything like this with my boots.
The soles of hiking shoes make it feel like I'm walking on sand compared to the combat boots which give a firm and stable platform. Hiking shoes let every little pointed rock assault my feet. There is none of this with combat boots. Cactus needles don't come through the soles of the combat boots like they can with hiking shoes. The combat boots have an energy return system that makes them rebound with each step while still absorbing the impact of each step. This more than makes up for any weight difference.
Moe, you should know I'm the only one of this forum who recommends the modern combat boots. I think I'm also the only one on this forum who has worn them. I don't know anything about any other combat boot except the Danner boot. Each style of Combat boots is made for different purposes, so you'd have to be careful choosing a substitute.
Danner boots tend to be true to the size measured with those things they have in shoe stores. There should be enough room in the toebox to wiggle your toes in all directions. There should be about a half inch in front of the toes. They should feel a bit loose in the toebox compared to what you may be used to with other pointed shoes.