If your toerail is already through bolted along its entire length and the fasteners are as easy to get to as you say, I would go with the aluminum. Getting wood to curve is not easy and the cost of knot free clear teak or mahogany might be as high as the metal (I have only purchased small amounts of teak, but have been startled by the cost). I have had to bend wood for smaller projects, it always seems harder than it looks. You will have trouble getting wood the length of your boat, so scarf joints will be needed, which makes the bending even harder.
Your maintentence concerns are real. The hardest thing to maintain on my 30 ft boat is the toerails. Remember they meet the deck on both sides of the rail, a total of 120 linear feet of wood to glass contact. This makes finishing, taping, cleaning etc an hours long chore on your hands and knees. The toe rails get the most abuse of any wood part of the boat, and therefore need the most attention. I would trade the look of wood for low maintenence metal any day.
Hopfully someone with more experience with alumninum rail instalilation will chime in, I will follow with interest.