Straight or curved makes no difference whatsoever to foot clearance. The wheel hub is in the same place: the only difference is whether the fork goes in a straight line between crown and hub, or a curved one.
On material, I know a number of people who consider forks with aluminium steerer tubes to be disposable items, to be replaced every 2 or 3 years before they fail through fatigue. They generally fail at the base of the steerer where it joins to the crown, and the consequences can be instant and nasty.
Steel forks generally fail more slowly, and you'd normally have steering or headset adjustment problems first. I know someone who rode back from Bristol to Cheltenham with his forks gradually bending forwards at the crown, until he eventually had to stop riding when the pedals hit the ground at the bottom of the stroke. He was in walking distance by then.