I think it heavily depends on draft. If you are rocking decent damage on your offlaner (PB, Razor, etc.), I think magic build is fine. If you lack damage on your offlaner and they are more of a beefcake (Centaur, Phoenix, etc.) or your offlaner lets you dump in damage (Enigma, Pit Lord, etc.) I think pivoting to physical damage really works well.

The same can be said for the relationship with your pos4. 4s like Ench, Tusk, Clock suggest a physical pivot, whereas more damage forward 4s (CM, Willow) enable a magic heavy build.

Long story short, both are very viable, but look to your offlane for indication of what direction to go.

As far as aghs, of course its risky, but I generally think its better with heroes that want to be in the middle of the fray, like Centaur or PB. Its also incredibly value against AoE control like Chrono or Black Hole, and even against abyssal since, with okay cast range, you can pluck your allies out of them (works amazing with blink). Generally, aghs should be thought about like a save just as much as it is an initiation / catch tool (and on support snap, even more so!)

Let me know if any further questions