Onlive:
pros-
Don't need to buy a high end gaming rig.
Easier to restart and start different games from wherever you are.
Official support of the gaming companies.
Less chance of technical problems due to using their servers and fast Internet connection.
Separate TV addon box available with HDMI connection for your living room.
cons-
Monthly charge.
Loss of freedom with using their servers etc.
Uses browser plugin which is just silly and might only work on Windows and Mac?.
Will mostly cover the latest games.
StreamMyGame:
pros-
More chance of them adding support for less common or older games.
More freedom as you use your own equipment.
Uses dedicated software which can be easily ported and will be platform independent.
cons-
Harder to start or restart different games without being near the gaming rig itself.
More prone to errors with relying on your home hardware and connection.
Have to pay out for a gaming rig yourself.
Harder to get working on a TV in your living room.
I'd rather use StreamMyGame for now. I really don't game enough to pay out a monthly charge for it