AMD cards dominate Nvidia in pretty much all password hash bruteforcing algos, even those that do not rely on bit rotation (bit_align). See http://golubev.com/gpuest.htm for example. It is true that another instruction helps in more cases (bfi_int which I talked about at http://blog.zorinaq.com/?e=43) but in general, AMD cards have a lot more raw integer and floating point compute resources (execution units) than Nvidia cards.