It does look larger, plus some of the details are changed- the generator protusion thingies on the side jut out further on the new model, and the top of the main stand is extended too. The stand looks to be wider.
Obviously the base is different too- the new one is utilising the power packs found in a lot of the new terrain kit designs, especially the Ryza-pattern ruins.
The new text reads 25 instead of 28. I don't know what the significance of that is

Perhaps it is a Mk25 containment field generator, rather than a Mk28? That would be a simple fluff explanation for the different designs.