I did write it before to you, most people on these forums are racers, racers have other demands than bashers like you, they even buy a plain chassis for a same price you buy 2 or 3 RTR cars. Racers need a reliable control with a most direct feeling, any cheap ass transmitter that has no framerate going lower than your DX6 pro 5.5msec is getting too slow for hitting the apex perfect every time.
In this case a 4PM does provide the same transmitting technology as the 7PX but in a less fancy housing with a less fancy screen. Only the feeling and mechanical adjusting possibilities will probably be better with the 7PX.
And no, I did not take a 5th morgtage for my T7XC, I could buy it from TAX returns Beside that, my T3VCS was becomming too old getting issues and needed a replacement. In case you did not notice, in my case they are so called "surface" stick type transmitters with which there is not much choice on the market.