Competition is good at all stages of the research pipeline; it's the alchemy by which base human fears and desires are transformed into technological progress and better lives. More competition means a greater chance of more efficient, effective new medical technologies; the more competition the better, I say.
One contest of note is that between the development of artificial replacements for body parts and the progression of tissue engineering (or regenerative medicine - the line blurs when the body parts under discussion are small, such as a handful of cells in the eye). Given equal funding and a standing start for research and commecialization, it seems plausible to imagine either a minaturized, implantable kidney-shaped lifetime dialysis machine or a fully functional kidney grown from your own cells arriving at the finish line first. We live in exciting times: the same advancing biotechnology that enables tissue engineering also makes it possible to replicate biological functions in other systems - and at ever smaller scales.
It's all in the early stages now when talking about recreating the functions of entire organs, of course. A good example of present day research cropped up in the MIT Technology Review recently:
There are several different approaches used today in the attempt to develop retinal prosthetics. But the basic principle underlying all of them is the same: by stimulating cells within the retina, vision sensations can be elicited in the visual cortex. This is possible because for some common eye diseases, like retinitis pigmentosa and macular degeneration, only the light-sensitive photoreceptor cells in the retina are damaged. This means other types of cells in the retina and visual cortex in the brain remain intact and fully functional.
Until now, the method of choice for repairing these cells has consisted of using arrays of electrodes placed near the retina to stimulate the cells electrically. The trouble with this technique is that, apart from the electrodes being larger than the cells they're trying to stimulate, there is no way to isolate the electric fields in order to trigger individual neurons without triggering their neighbors.
Encouraging the cells to grow tentacle-like dendrites between the cell and an electrode [gets] around this problem by creating a communication channel that stimulates the cell without invading or disrupting the structure of the retina.
The real payoff with this method, though, is the ability to make use of the preprocessing of the [retina]. Until now, most research has focused on stimulating the retinal ganglion cells, the large cells that feed signals directly into the optic nerve. But this bypasses all the motion-detection and edge-detection processing carried out in the retina itself by a network of neurons called bipolar cells.
My one complaint about all this is that, for all the rapid advance in capabilities, this type of work is directed at patching up the end results of age-related biochemical damage - plugging holes in the crumbling dam rather than preventing or repairing the root causes of those holes.