From Lanemaster :
RG -- 2.61
Diff -- .039
From BTM
RG---1.5
Diff/Flare ---- 10.1

which one is true ?
why there are so big differents ?

I think you're looking at "apples and oranges".  If the figures you're talking about from BTM are what's to the left of the write-up for each catagory, that's just their rating system, not the actual specs.

the vendor rating are the "real " numbers that correlates to actual mathamatical and quantifiable values.

the BTM numbers a rating system they created to judge I ball against another.

they both have merit. one is just numbers without any reference to the shell.

take a couple of pearl balls from different manufactures with similar numbers and their will be differences.

BTM attempt to bridge the gap and rate each manufacturer by their scale.

this has merit because strong MB balls, cores and shells design will have more to say about the natural hook shape that the numbers.

for an example the Big Kahuna has a lot more length designed into the ball so if you have slow speed pin up will be fantastic for length. tweeners and crankers may not want a ball with this much length. these balls and RG do not translate well into the pure math numbers.


I also find that smaller manufactures ball descriptions are more valuable than some other sources. I talking about at least 10 balls from three smaller vendors and all have been very reliable to there describe ball reactions.
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"deserves got nothing to do with it."
-- William Munny