I have every ATV model, but I have been disappointed in the ATV4 so far.
Most of the bugs have been fixed, but the ATV4 apps that are on the ATV3, like Netflix, HBO Go, YouTube and others, have horrible UI when compared to the ATV3. The one exception is the ATV4's Hulu, which, other than the slow start up, is an improvement over the ATV3.
Netflix UI is the biggest complaint of mine. Evidently, the ATV4 Netflix app is modeled off of the apps that most other devices use, such as Playstation, but trying to find stuff to watch is horrible.
I find myself using my ATV3 to browse stuff on Netflix, and then watching it on my ATV4, which is on the bigger TV.
The best thing on the ATV4 for me so far would be Alto's Adventure game. If I could get that on the ATV3, I would probably switch back to the ATV3 for good.
My advice for you, check to see if there are some apps that are on the ATV4 that you really want. If there are not any apps that look like you want, wait for the next ATV.