Forging vs Casting
Whitewater gear is required to go through a lot of abuse during its life, so choosing the right components that can take a licking and keep coming back for more will provide great long term value.
Aluminum
Forged parts (Frame Brackets, Oar Towers, Seat mounts, from Better Mounts or NRS) are all made to be tough and light. Forging requires a lot of force to form a heated piece of metal into the required shape. This intense pressure and heat create a part with consistent high strength, and allows the use of strong alloys.
Cast parts (Hollaender speed rail fittings for frames and oar towers from DRE etc) are heavier, and more prone to cracking. The casting process limits the types of alloys available to weaker alloys that are more likely to crack under heavy use. These fittings can be strong enough by thickening material to increase the strength of the parts, but their weight increases as well.
Stainless Steel
Forged and cast parts can be made from the same alloys, and show similar strength. The choice between forging and casting of stainless is primarily due to part geometry, cost, and quantity reasons, but as a consumer, the different between manufacturing methods is generally less important.
