I tend to think of this stuff from the cloudcracker.com perspective, which is all about cheap jobs rather than millions spent. I rarely do brute force because,

I tend to think of this stuff from the cloudcracker.com perspective, which is all about cheap jobs rather than millions spent. I rarely do brute force because, honestly, it's rarely necessary. But the single biggest factor in cloudcracker.com support of a hash format really is its efficiency in GPU space. For instance, right now I'm implementing support for the modern SHA-512 crypt() variation. It doesn't translate well into GPU space at all, which will end up meaning that I can only offer dictionaries that are half a trillion words smaller than formats which are fast on GPUs. So far the data I'm seeing indicates that differences of that scale in dictionary size really do make a difference on the success rate of the job. So for what it's worth, from that perspective, it is a factor.