Definitely the square one. Trucks are square. Makes sense to me.
Well, the shape is only really relevant to what I'll be trying to accomplish for the long term, which is to create at least one of possibly two or three generic bases to display armor related models on. This one will be an urban setting, with destroyed building remains and rubble. I had several Custom Dioramics and Varlindun building remnants, but sadly, most did not make the move here, apparently, so for the moment at least, I'll resort to an Italeri wall section. I do have lots of debris and stuff though.