The p3 is real nice... when it works. If you get one , get it at camping world and buy the extended no questions asked warranty ( where they drill you for hours and try to weasel out of replacing the thing as much as possible ), and when it poops out and you have to get it replaced, dont forget to pay extra again for the extended warranty on the new one, so you can go through it again the next time. . I'm on my third one now. I think I've spend more hours driving on my el cheapo spare that I keep mounted up under the dash than I have on teh expensive on and they both stop the trailers, big heavy ones , just as good
but the cheap one has never failed. Sometimes I think that they have grown to expect just a bit too much from one wire going back to a trailer.
Whatever controller you do get , I STRONGLY suggest mounting up a cheap backup controller with a plug in harness within reach, that you can unplug the main controller and plug up the backup going down a grade should the main controller ever fail on you going down a hill. I had this happen to me dragging a rather heavy silver Streak about 30 years ago off Tehachappi and I hit Bakersfield doing about 130
I was in severe need of an underwear change by the time that sucker ran out.
Thankfully these engines have VERY good engine braking and will hold a load back without trailer brakes if you dont start off the top too fast unlike a small gasser like I was driving at that time, but it still pays to play it safe.