Catback will be louder and sound a bit better, but most of the lower cost (and some of the higher cost) systems drone badly.
Bypass pipes won't sound quite as good, but still sound great and very little drone, if any.
Internal muffler bypass also sounds great and looks stock.
If you want to do the whole exhaust, you'll need to do the intake side as well before seeing any gains.
For sound only, I'd do the bypass.