Yep, there are pros and cons, and then some.
I have used them all over the years. Wood, Composite and Carlisle (aluminum). And there are wood/composites, too.
Wood is beautiful, it flexes well and ash oars are very durable. Probably only a rock snag in class 3-4 water will break it. But wood is the heaviest choice. If you can balance them in the oarlocks, you might notice little diff, but that is sometimes hard without the grips overlapping, thereby causing bloody knuckle syndrome (counter weights might be considered). And they're one piece, so if you break the blade, you're in for a whole new oar. Also, you've got the wood maintenance factor if you want to keep them beautiful.
I 'graduated' from wood to Cataracts several years back. Cataracts offer removable HD plastic blades/graphite shaft. I also have a pair of Sawyer wood blade+grips/graphite shafts. Take your pick, but the Sawyer choice is a little spendier. They are lighter, probably as tough as wood and have a nice flex. The blades (and grips on Sawyers) are separate from the shaft. The Catarcts come in very cool colors. About the only downside is the price. Shop around, but I have bought from CascadeOutfitters.com in Boise.
All I'll say about Carlisle oars is: they're cheapest choice and make an ok spare. I broke several hundreds of dollars worth of them in class 3-4 before going wood.
I have pair of 9' Cataracts for my DB and I use 10' Sawyers for my 17' oar raft.
rivergeek