It's because it's a custom build and the cost of £3000 that I am thinking so hard about it. There isn't one which has everything, each offers positives. In the end I'll be delighted either way that's for sure. I need a collection yours I reckon. Bit of everything.
Have you gone in to any instrument shops, and spent some time playing StingRay Specials with both maple, and rosewood fingerboards?
I'd be less concerned about tonal variations, than playability factors, such as navigation, and feel.
Admittedly a big part of the reason I prefer maple, is dependent on nicely figured maple, but from a practical standpoint a maple board with black dots is much easier to read in poor lighting conditions, than a rosewood / ebony board with white dots (particularly top lighting, especially at certain flicker frequencies, where the oscillating strings create a silvery blur, obscuring the white dots, which appear silvery too).
Of course we're talking nanoseconds of difference in terms of cognitive delay, but it can enough to cause you to actually have to
think, and derail things.
The thing is, the EBMM roasted maple necks actually have a lower contrast ratio between the darker board, and the black dots, than traditional maple - so you may find that you find it easier to see white dots against a dark board.
Like you say, it's a lot of money, so you want to make the right decision : I'm just bringing up that it not
all about the sound, the effects of which are negligible in a full mix - whereas your playing experience is very much influenced by the feel of the instrument, and by how easy (or hard) it is to navigate; which has a direct bearing on how good (or bad) it sounds.