Apologies if this is not factually answerable to date.
Of the two senses above, which would we be closer to being able to replace artificially?
Two people, one totally blind and one totally deaf – which one would have the greatest chance of having their disability remedied by either surgery or technology? Which are we closer to achieving – replacement hearing through transplant / implant / reconstruction or technological advances, or replacement eyes – through similar methods?
On what kind of timescale would be expect to be able to perform this, or could it even be done today if the money was right?
Well, there’s cochlear implants, which can be installed in congenitally deaf people as well as some people made deaf by accidents. They don’t perfectly replicate normal hearing, but they can help a good percentage of the people with nerve deafness. We don’t currently have similar therapies to help people who are blind because of damage to the optic nerve, though some researchers are working on cameras that link up directly to the sight portions of the brain.
It would probably depend on the cause of disability though. Someone who was blind because of glaucoma would have a better shot at being cured than someone who was born without the sound-recognition parts of their brain. Generally, though, I think deafness is much easier to cure now. Which makes sense, since sight is arguably a more complex mechanism, and you can get farther on the limited hearing generated by cochlear implants than the limited sight produced by brain-linked cameras (which AFAIK cannot reproduce color, and are poor at replicating motion, and haven’t been cleared by the FDA yet).
Right now, we’re definitely further ahead on restoring hearing. Those who were hearing, went deaf, and now use a cochlear implant report that, while far from perfect and certainly not what they had before, it really does restore some ability to hear. But, as pointed out, they do not work for all people. If the deafness result froms damage to the brain itself such an implant will not help.
We don’t have anything to restore sight in a comparable manner at this time.