This is purely anecdotal based on my experience having had both DirecTV and Dish 3 times each from 2004 until present. DirecTV, both with the old 3LNB and more recent 5 Satellite dishes seems to lose signal sooner and outages last longer than Dish with a 1000+ or 1000.4 EA dish. I don't know that it is only due to the microwave band they are using. It may also be the dish design, tuner sensitivity, or other factors. Now, that said, neither should go out in light to moderate rain. I only have really had outages when there is a strong storm between the dish and the sats, and they really don't last long with either company. I've watched TV with almost no interruptions during hurricanes with both providers.
Of course, Charter (TWC) around here has a problem of going out when it rains too hard/gets too humid as well. If AT&T Fiber had a better solution than the old Uverse, that would probably be the best solution for us to avoid outages, but there are other factors to consider.