I'd have to vouch for the plastic's on the Serpent cars. Very durable. Good mix of soft for durability but stiff for precision. Wear is very good, could go a season or two of racing every weekend before needing to replace.

The Aluminum knuckles improve the precision and the durability. But more so the precision. Going to the aluminium knuckles and caster blocks in the front can make the steering feel more precise, more direct. But I wouldn't replace until something breaks.