Difference between robotmesh.com, vexrobotics.com, idesignsol.com, etc for Ordering

What’s the difference between ordering from vexrobotics.com, robotmesh.com, idesignsol.com, and the many other vendors of VEX products.
They all seem to have the same availability of items and price.

vexrobotics.com is the official VEX store.

Robot mesh, iDesign, and a few others are resellers of VEX products in certain regions.