I remember doing this for someone else once, it's for a 7 foot tank but the results would be the same for a 9 foot. It should give you an idea anyway.
So a quick note, all these plots show displacement. The main purpose of the bracing is to minimize deflection to not only stop the glass from breaking but minimize distortion. So obviously the lower the max displacement the better the brace.
Tank with no bracing for reference:
Max Displacement = 2.2mm
Tank with single large center brace and small euro bracing (standard design)
Max Displacement = 0.26mm
Tank with Euro Style Bracing (4")
Max Displacement = 0.36mm
Tank with Euro Style Bracing and two smaller center braces (4")
Max Displacement = 0.26mm
It's clear that the large center brace works effectively and that's why it's common practice for large standard tanks like the 230. A 4" euro brace works well but not quite as good, adding two additional center braces matches the large center brace and gives you better access and better opportunity for lighting. A larger Euro brace (5") will also likely match the large center brace but in the end the exact style and layout of your bracing will depend on your tank size, lighting and access requirements.
All in all you can't really say one is stronger than the other, both designs have the potential of being equally strong it just depends on the size. Also for a longer tank the results would be similar since you would use thicker glass.
HTH