Depends on what you want to accomplish, cost and sound. SLP makes nice systems, Magnaflow also, I've had both, Borla is a nice set-up as well. Magnaflow and Borla have a similar sound level, but the Borla is adjustable, SLP is loud, even the quieter ones are similar or slightly louder then a Magnaflow. As for ORY, Pacesetter makes a nice one for their headers that tukes up nice, Stainless Works makes a more universal one that is designed for maximum flow but I've never seen one personally. The redesigned Texas Speed ORY fits much better then the ones from 4-5 years ago.
So basically decide how much you want to spend and how loud you want it.