Why is the m1128 9.7 br in ab but 10.3 br in rb

it’s weird because most vehicles at that tier have the same br between the two game modes

You sure? 10.3 RB IN A RANK VI?

i was talking about it’s Arcade battle rating

Well, 9.7 in arcade is fine.

Because in AB it has a big sign above it for all to see “I’m a light tank - come kill me”

So do many other light tanks, and most get a single BR, if even that.

Not necessarily. Depends on if the tank is more effective when it’s harder to spot.
Examples below …

m24 = 3.3 / 3.7
m18 = 5.3 / 6.0
m41A1 = 6.0 / 6.3
T92 = 6.7 / 7.0
XM800T = 8.3 / 8.7

Concept 3 = 4.3 / 4.7
Eland 90 = 7.3 / 7.7
Scimitar 7.3 / 7.7
Fox = 7.7 / 8.0

IKV 91 = 7.3 / 8.0