The zip in windows are definitely better than the sewn in ones and much cheaper to replace when they go misty/crack.
One thing I did for my old window when I first got it was to use some car polish or t-cut (can't remember now but google it) to polish the outside surface and it radically improved the clarity. Not something that you can do too often but got rid of/reduced the big white crease mark mine had at the time
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