Although soaring sales of Amazon’s Kindle Fire and other low-priced tablets trimmed Apple Inc.’s media tablet market share in the fourth-quarter, it was Apple’s own newly introduced iPhone 4S that proved to be the strongest competitor for the iPad during the final three months of 2011. Apple shipped 15.4 million iPads and iPad 2s during the fourth quarter of 2011, according to the IHS iSuppli Disp