I'm not sure what we would be buying (I assume stock or products from the company). Anyways, I selected Google and for a reason.
Apple is already a large company and right now is at a stand still in terms of product sales such as the (i) product line. Apple is losing steam to the Android based systems and fast.
Google Android, while the OS is free and the SDK is free, the droid opens up a vast new market and that includes for advertisers. I see Google rising beyond their all time high and reaching a level nobody would have expected a year or two ago.
Microsoft... It will continue doing what it does. Right now it doesn't matter. What does matter is the battle between Apple and Google.