I have found that these two work quite differently. For my hand, the Thing Returns covers the same number of boards as the Thing and handles carrydown just as well (I keep both in box condition). The Thing is a smoother ball and needs more oil to get through the heads and midlanes cleanly. It also wants something more of a "bounce" area -- either very sharp backends or a relatively hard wet-dry block -- than does the Thing Returns. However, the Thing Returns is angular and can be aggressive on the backend, so if you want maximum forgiveness to the pocket, the Thing is probably going to be your choice. I find that for most conditions, the Thing Returns matches up better, in the sense that by holding more of its energy to the backend, it allows me to carry more and score better, while the Thing provides me some room where the lanes are overblocked or dished out.
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"I don't mind if you don't like my manners. I don't like them myself. They're pretty bad. I grieve over them on long winter evenings."