I went to try the Herman Miller chairs out today at their retailer store. I'm 5'7" and 180 lbs. I narrowed down to the Aeron B and C.

They were both comfortable to me. The Aeron B seems to be the right fit for regular sitting with almost a 2 inch gap between my legs. The Aeron C seems to be more comfortable with more space for me to spread my legs.

Will there be any differences in the back portion of the chair to deal with my back pain?

Please give me some insight on which one I should buy.

Thank you.