stainless steel vs aluminized steel, mandrel bent vs regular bent
have a local shop that does beautiful exhaust work. if its only a mild 318 and you aren't upgrading any time soon then i would just get the local shop do it and not worry about mandrel bends or stainless. tti systems are nice also. pricey though. my exhaust shop can do the system for half what the tti cost. i would want to see what kind of work the shop has done and decide from there.