The B4 and X-6 are visually very similar at the front, being that they use the same components.

The wheel base on the X-6 is shorter in these photos by a few mm, I imagine this mostly comes from the spacing used on the hubs and wishbones.

I have tried to show the greatest mass - the cells and motor - and how those are positioned in both cars. You can see the weight is far more central on the X-6 leading to a quicker rotating car.