Not tried a 5 AM, but I do own a 2010 5 and Alpine 160, and although I am no trail god, I do prefer the 160. I am 5’10” and both are 18″, yet for some reason, I feel more comfy on the 160. Climbing wise, the 5 is lighter, but also more prone to the nose getting light (150 Revs) on steep bits. The 160 goes up anything at its own pace without drama. Its when you point them down that you notice the difference. The 5 is very good, the 160 is AWESOME.
Sticking 160 forks on a 5 will help it towards performing like an Alpine 160, but its a compromise !………shorter travel rear, not so good shock/travel ratio, and the split clamps on the bearings don’t help rear end rigidness either, all add up to a back end that will never cope a swell as the 160.
The only area I find the 5 better, is on twistier singletrack.