Yes, I actually do have tasks for each. I have been doing some work with MAPI (messaging API) and see an opportunity to create a subscription based website doing electronic forensics. That would be on the c++ side.
On the iPhone/objective-C side, I have a project in mind integrating iPhones with a dieting website. So many choices, so little time...
Plus, does it have to be "either/or"? Spend a few days learning one, spend a few days learning the other. You should have gotten to some non-trivial level with each one and more of a taste for what you actually want to do.