I agree with what the previous poster said. I like the look of the wood and the functionality of the aluminum. The aluminum would need to be through bolted along it's entire length while you would only need to through bolt the wood at the track. So a key is how much access you have inside for washers and nuts. Depending upon the sharpness of the bends, you might have less trouble with the aluminum but you may need to make a clamping jig or long pipe clamp to pressure them around the curves. The wood might need some coaxing with strategically applied water to help it bend correctly, again using your job-made clamps. Don't forget with either material to use caulk (life-caulk not 5200) to keep water out of edgegrain of wood and help with structural adhesion for either. I'm thinking you might have an easier job with replacing it with wood simply due to the access under the toerail around the length of the boat.
Once you remove the old material, you will get an idea of how the toe rail is presently installed. If installed with wood screw like I imagine, you might need to fill and fair to redrill the holes for best bite for the new screws. While it seems like a big, complicated job, breaking it down into segments will help it go smoother and you should enjoy the result. It's a very pretty boat.