I haven't yet tried a Natural, but most reports indicate it is a ball that needs a good deal of dry to work with its stock cover.

I did own a Thunderflash and even with a high gloss polish, this ball hooked a lot for me. In fact, I guess I threw it too slow, as I neeeded medium oil at a minimum. I did a lot better with the Thunderflash Pro which had a different core and a lot lower RG differential and, this, lot less flare. I still needed to polish it up. I used that ball for a quite a while. That one I liked a lot.

So I suspect that the Thunderflash is a notch stronger than the Natural, or would be for me. I cannot say, since it's been so long, whether the difference is only in the core and its higher differential.
--------------------
"None are so blind as those who will not see."

I owned a Thunder Flash Pro and loved the reaction, but it definately didn't have a urethane backend reaction it was WAY more flippy than any urethane I had ever drilled in the past.
--------------------
-Chris: DJ's Pro Shop : Auburn, MA

NATURAL is much smoother down lane than the THUNDERFLASH ... assuming both are box.  Of course, NATURAL box is much rougher than TFLASH so could be a factor.  Have not shined my NATURAL and don't intend to so someone else can perhaps provide that comparison.  I struggled with the TFLASH cuz it was sharper than what I wanted off oil line.  NATURAL is more like a BLUE HAMMER of long ago vintage, which is exactly what I was asking for 10 years ago!

My polished natural is very smooth.