I went away from slugs for one reason, the fact that on the box of a new ball it says that putting a slug in the ball will void the waranty if it cracks. but it also says the same thing about finger grips. When I went away from finger grips I went away from slugs at the same time (even though I have NEVER had a ball crack that had a slug in it Knock Knock Knock). I've just recently started having some real problems with getting out of the ball consistently. So I'm currently in the process of reverting all of my equipment back to the slug. So far it has really helped me and having a consistent feel between equipment is such an important part of a more advanced player's game. If I were you then I'd go with the thumb slug. I've heard that most proshops are really good about replacing the ball if it cracks because of a slug or grips. Hope you have good luck with this.
Jeremy
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"Strive to be perfect, that is afterall the only way to become perfect."
"If you compare yourself with others,
you may become vain and bitter;
for always there will be greater and lesser persons than yourself.
Enjoy your achievements as well as your plans."
Taken from Desiderata
Proud user of Columbia 300 and Visionary Bowling Products