Hi,
In my opinion:
Aluminum if you are going to fish the Salmon River alot. The rocks are nasty there. Aluminum is noisy. Wood requires lots of maintenance. Fiberglass is easy to repair, I put a gallon of gelcoat on the bottom of my Hyde after 8 years of 100 days per season use. It looked brand new. Highsider is safer.
Lowsider is great for the Delaware, they are easy to get in and out and do not sail in the wind so much. I am not all that comfortable rowing my Hyde low sider on the Salmon River. I do it occasionally, but a bigger high side would be safer.
Side or floor anchor system?
Our Hyde has a side anchor and the Clack has a floor anchor. I like the side anchor system for two reasons. First, the rope is always right there and easy to grasp and feather out slowly and quietly. It is also easier on my back. The downside is that the person in the back has to be careful about getting fly line trapped in a pulley. Floor anchor system tube can freeze in cold weather.
Oars: Standard oars vs. counterbalanced. Counterbalanced have a chunk of metal in the handle and it makes the oar balance at the oar lock. That way you are not using energy to "hold up" the oar. IT just rests there with no effort. The downside, a slight one, in my opinion, is that the oars tend to float on the wwaters surface and do not act as rudders to stabilize the boat while at rest. Composite blades or plastic or wood? Not huge differences here, but the composite blades tend to have more surface area, so you get more bang for each stroke.
New vs. used: Well maintained boats hold their value and can be a good deal. Used boats on the Delaware typically sell for $3000 - $5000 depending on age, use and extras. There are usually 6 -12 for sale every spring. The manufacturers will sometimes make you a deal if they are getting a boat in trade. Rather than ship a used boat back, they may sell it to you.
I rowed a Hyde for 15 years and still prefer them. They row easy and turn on a dime. Probably not as comfortable for the fishermen, as they do no have the room of a clack. The Clack is a bit more awkward to get in and out of, due the placement of the back knee brace. Some of the newer models may have fixed this glitch, I have not been in a newer boat the last couple of years.
Boats are just like cars. When you are 16 and get your first car, if it has four wheels and runs most of the time, you are happy. As you drive a bit more, you understand the features you would like to have in the next model. If you rent a couple of different ones, you may get an idea what features you like.
Storage areas, rod holders, padded seats, cup holders, etc. are just some of the extras to consider.
Have fun!!!
Jim