To me they are both very "accurate". Neither could be called especially warm. Both have soundstaging about as good as it gets for MM carts. The AT's top end is a little more textured, the Ortofon very clean and dry. The AT has lower surface noise, the 2M black and the 2 M's in genral are warts 'n all cartridges- if there is an imperfection with the vinyl or the recording, the 2 M's reveal it. The 2M's are very high output, about 2Mv higher than the already high AT, and so may actually overload some phono stages- check compatibility if possible. One British mag measured the 2M at close to 8Mv output! A guy on ebay sells the black discounted, and the AT street prices have gone up, so while the AT is still cheaper, the price difference is not as great as it was. Overall the AT is a safer choice IMO.
