Vlad Savov has really done a great job of laying out the pieces of this puzzle you need to think about and in what order.
Ultimately, the number one lesson in photography is that there are always tradeoffs. If you want the best possible image quality, you’ll need specialized and bulky equipment. Should portability be your highest priority, you’ll simply have to accept that some photos and creative ideas will be beyond your reach.
In other words, there is no one camera that’s perfect. This is why I use three: iPhone 4S, Canon S100 (and S95) and Canon 5D (at some point upgraded to the next Canon 5X). Each has its place.