Well, from my experience.. CS rocks. I know nothing about ST other than seeing them at Sportsmans Warehouse.
I guess the only thing I have an issue with is NSF certification. I don't know why CS can't do a cert on a box like the AQ for a reasonable price. The AQ is, IMO, a step above all the other residential models. AQ should fall into the tweener category
ST 1500-C is more expensive than the AQ but it is NSF certified. You can' get into CS that is certified for less than an arm n a leg.. I'd be willing to pay a couple hundred more for that cert.