Urethane Quality

[SmoothG]

Are there different grades of Urethane?  I play the OnCore Elixr and am very familiar with what it feels like in my hand. I had someone gift me a dozen Srixon Q-Star Tours and the urethane on these two models is very noticeably different. The Srixon feels more slick where the OnCore is tacky.  Maybe I'm weird but I bit the balls and you can notice a difference in the cover hardness.  I'm wondering if one of these may be more durable than the other or why there is such a difference in feel and how does this affect performance?

[storm319]

Two different approaches to urethane covers:

Thermoplastc Urethane (TPU) - liquid material is injection molded similarly to how ionomer covers are produced. Ex models: Bridgestone Tour B, Callaway Chrome Soft, Srixon ZStar.

Themoset Urethane - components are mixed in a cast mold and a chemical reaction occurs producing the final solid state. Ex models: Titleist ProV1, TaylorMade TP5.

Thermoset casting tends to produce thinner, softer, more resilient covers but is more expensive as the process takes longer per part, requires additional painting steps, and the material is not reusable unlike TPU if something goes wrong.