A few things. First, I agree, as you say, they do have screens. I have Andersons and the screens go on the inside. You can remove them if you like. I have most of them out and only use them on the few windows that I regularly open.
Something no one has brought up is how they fit with the style of the house. IMO, that is a big issue. Casement windows tend to be used on more contemporary, modern looking houses as opposed to say a traditional colonial. If you put them on a colonial, I think they would look weird, out of place.
Another aspect that I think is relevant since the OP is looking for ease of operation, IDK how all the new ones work, but the Andersons I have rely on two latches, one about 1/4 way down from the top, other 1/4 way up from bottom to secure the windows. You don't have to have them fully secured all the time, but for security, if it's winter, etc, that's how they get locked, if you will. The crank moves them in and out and you can just close it, but if you just do that, while it's not going to be obvious the window is wide open, it is going to be a lot easier to gain entrance via a pry bar, etc.
The reason I bring this up is that OP should take a look at some in the sizes and see how easy it will be to reach the upper lock lever. In most of mine, it's easy. But I have a couple, eg over stairs, where it requires a stool. But then again, it depends if you need to open those or not. Also now that mine are 30 years old, on some of them, if you just wind it in with the crank, one of the latches may not reach because the window isn't quite closed enough. You have turn the crank harder to try to pull it in another 1/4", etc and I suspect that is what leads to some of the crank failures.
All in all, the modern double hungs that I've seen have been very easy to operate. Nothing like the old wooden ones that got stuck big time. I'm not sure that the opening closing is so much of an issue. The OP should go try some at a home center or window store to see how well they work.