They both sound like quite similar rackets to me. What are the main differences and is the AT900T worth the extra money?
forgot to add the at 600 has a flexible shaft (similar to ns6000) At900t has a stiff shaft (similar to ns9000s and arc 10)
You need to try it to decide. My wife gave up her NS8000 and loves AT600 now. Since you do not have too much of idea on their difference, I will suggest AT600 for the user friendliness...