I've used a couple different kinds of wood, aluminum, brass, delrin, steel, and stainless steel rods. I have not got to try fiberglass, and don't have much desire to. I will say right off the bat that that I have only bought one gun I was happy with the ramrod, and that was on an unmentionable, with a nice aluminum ramrod. Every wood ramrod I got with a gun was either chincy or had bad ends, or both. One I had used was (unknown to me) a hardware store dowel with a brass end glued on.
By far the worst is Delrin. Whoever decided that this was "unbreakable"... well I suppose it wont break. It won't break in the same way a cooked noodle won't break. But at the end of the day, ramming a ball down a barrel with a cooked noodle sucks!
Brass is a less than desirable ramrod. It is not going to break, but it is not as strong as steel either. At the same time it is very heavy for its size.
Steel and stainless steel ramrods I do like, but with the caveat of a bore guide. I really love the stainless range rods from Track of the wolf that have a brass bore guide, and a nice wood handle. Pro tip- pin the handles by drilling through and using roll pins to pin them to the rod. If you don't, one day you will pull the handle off when swabbing, and have to call it a day.
Aluminum is a modern standard. There isn't much to say, they work. Actually I will separate into hollow and solid aluminum. I prefer hollow aluminum, as it it far lighter, but still plenty strong. I've never broke one anyway. The hollow ones use push in ends. Do like with wood, both epoxy and pin the ends, or they will pull out. Solid aluminum works fine too, and is not overly heavy.
Now in the past I was more in the aluminum camp for the carried rod (on the gun). Over time I am drifting more and more to a well built hickory rod. By well built, I mean built by me. I've never found one sold I like. I buy hickory dowel from Track of the Wolf, the good stuff that is hand selected for ramrods, which doesn't have any runout. I then attach whatever ends I like by grinding down the wood ends to barely fit inside the metal ends (aka tips), and then a few slight grooves in the wood to help the epoxy get a real good grip. Inside the rod ends I take the roughest sandpaper I have, about 80 grit, and scuff the insides of them. I then epoxy the ends on with something good like Devcon or JB weld. After dried, I find a decent sized copper wire, which I have plenty of solid wire, and 10 gauge works good. I then drill a hole just a little bigger than the wire through the rod end, and slightly chamfer the hole on each side. I cut the wire just a little longer than the rod is wide, set it on a vice, and lightly peen the wire ends to essentially make a copper rivet. To finish, file the ends flush, sand the rod, and coat (I like linseed oil).
I find a hickory rod put together like this is extremely strong and stiff, yet is about the lightest option out there. It looks good to boot. I use the stainless steel range rod for most things, but the carried rod gets used as well.