Good morning Grim!!!!!!!!
Just like any other form of r/c, you'll find probably as many opinions as you will find noses - I've found Baja owners to be very strong in their beliefs!
I can generalize to a great extent by saying that the 'performance' exhaust systems that I've heard are ALL noisier then the standard 5B exhaust. The standard SS exhaust gives good performance but it's pretty noisy - not sure if there are any 'deals' out there in it or not but mine has proven to be durable (exce;t for thos times when I've been 'bumped' by other buggies)
and it's quieter then a lot that I've heard.
Since I only race mine, it's hard for me to come up with upgrades for bashing - the 5BSS is durable for racing and other then wheel failures it's been a joy to own and race!
Hope you enjoy yours as much as I've enjoyed mine!