The main benefit of Pro is the resolution improvement , so you really need the new screen. In some 3rd party games there is option for higher framerate (like Hellblade or Tomb Rider), but my personal preference has always been higher resolution.
My Pro is also noticeably more silent than launch PS4, but I believe Slim is the most silent of all PS4 versions.
The choice of the screen is where I would put focus on. TVs are the only reasonably priced option for 4k HDR. I swithced to Pro when it launched, and I decided to move from TV to monitor, and I bought Asus 4k 60Hz monitor, no HDR. Monitors have very low input latency, and I have found this solution to fit me best. However, if you are set for TV, I recommend oo check for a low latency version. There are huge differencies, ranging from 20ms to 60ms. Monitors are typically less than 10ms. Input lag is the time between the monitor getting the input from hdmi to the point when it is on screen. This istypically the mid value. There is actually a difference between top, middle and bottom of the screen.
The reason why TVs have higher input lags is the image processing in the TV, and for normal watching of films there is no impact if the TV spends time on optimising the image, but in games of course you want to see real time.
