Being one who has actually owned and used both, mostly using the framed sliders, I see no real advantage to the framed windows other than the fact they do not protrude past the shell when open. I am not considering the fact a few of the frameless have had issues, as ours so far have not.
The frameless awning style look better (though not the top deciding factor vanity does play in there some
), they operate nicer (a simple easy to use crank instead of having to slide the window), are better to use in the rain, and offer just as much ventilation.
In most cases folks definitely justify their choice, as they used their own reasoning for their decision. In many cases though, like these windows, removable power cords, etc, opinion is not based on actually using both, only using one option and just making a best guess on the one they haven't used. In the case of this window decision, I bet the vast majority of those who have had both would still choose the frameless, despite a small few of them having a problem.
The awning though is a more contentious issue with the pros and cons of both having a much broader range and more impactful of factors to consider. I love most of the things the new awning has to offer, but miss a couple of the ones the old had.