We have the company developing the 'hardware'
We have another company developing software
We have BJ and Bally's making 'compatible' chips
We have companies manufacturing microchips also

As Gene said earlier - they will all become obsolete quickly as each advance in technology is made.

The original question was 'who should I invest in'
Gene gave the answer to that also - 'welcome to the 21st century'
IMO all the existing gaming companies will have to compete and the biggest will come out on top in the long term but not necessarily the short term.

Mikhon could be a good bet in the short term - the far east always seem to take a small step ahead in technological developments and there is a window of opportunity before anyone else catches up. (I am talking 'hardware - wise' here)