Back-UPS ES vs. CS?

[BillP]

Just wondering if anybody can comment on the differences between a 500VA CS unit and an ES one. I know what their marketing material says am know the specs, but all in all their very much the same I find. Are there any major differences, perhaps in their managability or features that aren't posted on the basic Features & Benefits page of the model's wbsite?

Basically I'm looking for a reason why a customer would want to buy a CS model when an ES already provides the same amount of battery runtime.

Thanks very much.