Actually i think especially in regards to the cuda version of bitcrack, the number of cuda cores for the specific card is really important, and there is actually a bunch of older cards with some great numbers here, for ex. the GTX 680 have 1536 cuda cores, which also happends to be the number of cuda cores for the GTX 770.
Provided that programs allocate memory with the full grid size. The grid's Y axis has been pegged to 128 for a long time until some newer cards introduced a 256-card Y axis. And some programs still assume a 128-core axis and have it hardcoded so clearly those aren't making use of the entire grid.