Nice graph. 
As I am much more into naturals the whole Chelsea vs Beshine discussion is more of a diversion and I find will be difficult to lock down unless some fairly scientific measurements are done. The high likelihood that any numbers we get from the women are suspect and variable depending on circumstance makes the determination problematic.
From a purely social approach I would say that Beshine has greater volume now and has from about 2012 on. I anticipate that we are approaching the end of Chelsea's massive phases and that she will maintain a slightly more manageable size for the next few years before reducing again to "simply huge" in her late 40's.

I tackled this calculation over in the Breast Rating thread.
Here:
http://forum.bearchive.com/index.php?topic=9992852.msg10348577#msg10348577Note: math error reduced Chelsea and Beshine by 2 cups - this has been fixed. **
At the moment, and using the best most cross-referenced data, Chelsea Charms is slightly larger in volume and % of body mass that is boob. Beshine is very close behind however has larger tatas for her body proportions / build.
I know there is a good bit of confusion about values, units, amounts, etc. There is also the tendency to exaggerate and use hyperbole when dealing with women with such cartoonish dimensions. I did some digging to get as close to verifiable numbers as I could and back-checked them to see if they were even logical or physically possible.
The trick was to lock down three values, height, weight and bra size for the same moment in time as their breast size fluctuates so much. I also would reverse calculate from other concurrent dimensions to see if I would get the same results. For example, I would find a report of the total distance around Beshine or Chelsea which happens to also be use in bra size calculations. From that I could determine if the difference between that value and their band size would generate a bra similar to the one they state. Essentially could I "back into" their advertised size and get the same results?
Another cross-check was to look at their stated starting sizes, usually something they do not exaggerate. I could then "build" up from that base to see if stated numbers were even viable.
This is what I determined:
Chelsea at
Bq = 793 **
Advertised size 153XXX = 153cm (60") & XXX = known exaggeration and meaningless
Advertised volume at that size = 7000 cm^3
Bra size band = 34
Bra size cup = XXX is a Z cup or +26" above band for a total of 60" around which is 153cm (see above)
Height = 5'-2" (actual height)
Weight = 178 lbs (actual weight)
Breast size for a 34Z bra
Breast diameter = 31.75cm - widest expanse across both breasts apx. = 64cm (25.2in)
This means that her chest will extend over 8in on each side of her torso
This is confirmed photographically with items of known size and her height
This yields a breast volume of 8357 cm^3
Most recent fluid expansion up to 10,000 cm^3 actually works with these numbers
Assuming the 10,000cm^2 claim less the reported drain down maintenance 1000cm^3 and 590 cm^3 base tissue
10,000 - 1000 - 590 = 8410 cm^3 a difference of 53 cm^3
Combined breast weight = 30.08 kg which matches the reported max weight (30kg) at this size
Conclusion: Although there is a bit of figure and units trickery the reported volumes are in keeping with actual size. Due to her more open reporting and longer duration in the public eye her numbers simply come across as more accurate and representative.
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Beshine at
Bq = 856 **
Advertised size 59Z - interesting as this is almost the actual Chelsea size (60Z) when converted to real values
Advertised volume at that size = 10,000 cm^3
Bra size band = 32 (suspect, see below)
Bra size cup = 59-32=27 not 26 therefore the Z cup designation may be off by 1 cup or 1 band and the odd number designation is off by 1 for a bra size - most likely 58. 58-32=26 = Z cup.
Height = 5'-6" (actual height, 4" taller than Chelsea)
Weight = 79.83 kg (actual weight)
Breast size for a 30Z bra - adjusted to maintain a true Z cup designation (sister size)
Breast diameter = 30.03cm - widest expanse across both breasts apx. = 60cm
This means that her chest will extend over 8in on each side of her torso
She will look very much like Chelsea.
This yields a breast volume of 7088 cm^3 however could be 7705 cm^3 if at 59Z size
This is very close to the 7000 cm^3 base maximum confirmed for Chelsea without serum expansion
Combined breast weight = 25.52 kg which matches the reported max weight 55lbs or 27.5lbs ea.
This seems high as the reported weight is only 20lbs each.
Conclusion: Beshine (Mayra Hills) has some odd and most likely exaggerated values, but not by very much. She has a greater disconnect between her various reported numbers and they do not cross-reference as well as Chelsea's.
I would have to say that she may simply be trying to hit a Z cup which alludes to a XXX cup for marketing.
Her slighter build also pushes her right into the proportionality of Chelsea.
Summation:
Chelsea advertised at 10,000 cc probably hovers around 8357 cc due to fluid accumulation
Beshine advertised at 10,000 cc probably hovers around 7705 cc or more depending measurements
Chelsea has a more breast shaped chest with more sag and elliptical deformation which hides their full size unlike...
Beshine has a spherical installation on a very slight build so she simply reads larger.
It is interesting that both women are so close in actual "bra size" - essentially a cup or band size difference.
A 10,000 cc would require breasts 6 cups larger on both which is a large volume change at these sizes.
10K just reads more impressively, as does XXXcup or 153 which are not really helpful in this discussion.