BJ4 v.s BJ4WE

[Sensory Overload]

Just wondering - is there an any advantage(s) between the two chassis other than battery layout?? I just happen to have the BJ4 non-WE and am thinking of the conversation kit for next season. Do I really need to upgraded? I already have a ZX5 with a similiar battery layout as the non-we. The reason I'm asking is that the XX4 over the newer XXX4 (so I've read) has a clear advantage on rougher tracks. SO