I made the step from non-slug to thumb slug almost 2 years ago, and it was a progress for me. The only ball without a thumb insert is my polyesters right now. and I keep it this way because of the familiar feeling.
I prefer urethane slugs, which are quite hard. I have also tried softer vinyl material, but that was an ugly thing. The urethane stuff can be easily adjusted with a file or sandpaper, and it give good adhesion to tape. I also prefer white thumb inserts because the help me watch the ball's lane reaction, when it migrates towards its PSA.
The biggest benefit I see with a thumb insert is taht you have a material base that offers the same grip in any ball you have - as long as you keep it consitently. Unless you use molded thumb inserts, the balls might still feel a little different each, since not every ball can be drilled and prepped exactly the same. But the differences from "pure" holes is quite big, IMHO, and the feeling when switching between them is far better.
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DizzyFugu - Reporting from Germany
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