I had the first set of PPE DPs. Mike and PPE used my car for development. We found ceramic coating made no difference (I got ceramic for aesthetics and to match my hotpipes). All the following was done on stock tune in my '13 SHO. We found overall power increases of 12AWHP with catted and 17AWHP with non-catted.... All dynos same day. 3 pulls for each set of DPs. There was equivalent TQ increases on both sets. The earlier onset of usable power was the thing that made them fun. For what ever reason the powerband really started at 2100rpm or so OEM ...and more like 1600rpm on both the catted and non-catted PPE DPs. Both LMS and Unleashed have tune mods for the DPs, maybe others too, but the point is that you can expect a little more low end and overal power increase than I state above with a tune. I have not dynoed testing this mod alone since tuned.
I do not notice any change in noise driving, but the exhaust note is a little more authoritative idling... It will not sound like a V8. I get just a hint of drone at idle after warmed up and the idle drops to 600 or so (almost inaudible even with the radio off), but it disappears as soon as I add any throttle ...none anywhere else. So essentially no drone.
I chose catted because of living in an emissions state and with the Magnaflow high flow cats you pass visual inspection due to the CARB number on them. If you are not into self tuning: the catted also will not set a CEL. Most of the tuners are turning off the downstream O2 sensor (on the DP) with non-catted DPs to prevent the CEL, which will come back every time a driving cycle is done even if cleared..... If this sensor is off, at least in AZ, when the emissions guys plug in to the OBD it tells them the emissions (O2 sensor) is not working and you fail the readiness... I went catted so I don't have to changes DPs back to OEM for that. My dealer has no problems with them... Just complimented the appearance and workmanship... They look at them every oil change since I have 7 yrs prepaid factory maintenance as part of the purchase of the car.
Pick your brand... But do it... The factory DPs are incredibly convoluted, have flat sides and are clearly more restrictive. I am still running stock exhaust including 3rd cat other than this.