I'll warranty anything I put up outside against failure. ACM on a wall will be fine with enough screws + silicone. 080 is better, as you can get away with just lagging corners and no adhesive, usually at the customers discretion as to what they want the wall to look like when the sign is eventually removed.
ACM does have a tendency to tear, just try scoring and folding a piece to watch a dramatic failure, but more than that, a screw will only support the surrounding ~2 square feet of acm, so something like a 4x8 will get screws every 18 inches around the perimeter, plus the silicone. Same thing in metal would get the corners, and maybe one in the center if it wasn't folded into a pan.
For fun, screw a 2x2 square to a wood table in the center, and rip it off the table. The wood and screw will be fine, likely not even bent, the acm will just rip apart. Wind is the biggest factor, obviously, due to vibrations more than gusting, and if it's making the panel move back and forth, the acm will be whittled away by the screw until it gives. 080 or 090, or even 063 are stout enough to bang around for years before they give. Heck, there's a 080 panel hanging on my way between work and home, 24x36 with two S hooks. Every other storm will blow it off one hook, so it's flailing around in the breeze beating the post, and every time I see it I stop and re hook it. The print is looking rough, but the metal could be reused. If it were acm it would have been toast years ago.
