If this is something that doesn’t matter to you, and you only want a stable and safe pull up bar that will last you a long time and will be able to sustain a great amount of weight, then go for the wall-mounted type. The telescopic one is also a great solution if you are looking to minimize the damage. It will leave marks on your door frame, but there will be no holes afterward when you decide you don’t want to use it anymore. However, keep in mind that there aren’t any pull up bars that won’t mark your doorway or your walls. And if you happen to find any, it won’t be able to hold up a lot of weight.
Another thing to do is the measure of the thickness of the trim as well as the door frame width. Even though this seems like a piece of trivial advice, you would be surprised to hear how many people have bought a pull-up bar thinking the dimension of it is universal.
However, you should also consider your favorite exercises that you would want to do with the bar. If you want something other than pull-ups you should take a multifunctional pull-up bar that will allow you to do so. If you want to also make push up, for instance, you should take a bar that can be placed pretty low. If you want to make abs exercises on the other side, you could choose a fixed pull-up bar as well.