Without knowing what model of ER, I would say you should go with B, the G2 is bigger and better than the the G1. I can understand wanting to go with your favorite local fish store. But for the price, I would see if they would be willing to get you an Octopus skimmer. A NW-300 should sell for around $250 to $275 at a local shop, and is about the same size as the G3 and is a good skimmer, and with a few mods to the pump is a great skimmer for the price.
I always try to get the largest most powerful skimmer I can and go much larger than you think you need.
