Amazon vs. Microsoft: 1 Key Metric Identifies the Superior Artificial Intelligence (AI) Cloud Stock

Amazon is positioned as a superior investment opportunity compared to Microsoft, driven by the accelerating momentum and margin profile of Amazon Web Services (AWS). Although Microsoft Azure posted a 43% revenue growth rate in its latest fiscal fourth quarter versus AWS's 37%, AWS has exhibited a significantly stronger acceleration trend, climbing steadily from 20% growth in Q3 2025 to 24% in Q4 2025 and 28% in Q1. In contrast, Azure's quarterly growth trajectory has remained relatively range-bound between 39% and 43% despite massive capital expenditure investments. From a profitability perspective, AWS plays a transformative role in Amazon's overall financial structure. With AWS delivering an operating margin of roughly 39%, its rapid expansion significantly outpaces Amazon's low-margin e-commerce operations, effectively expanding consolidated corporate margins and accelerating bottom-line earnings growth faster than revenue. Conversely, because Microsoft Azure carries lower operating margins than Microsoft's broader enterprise software business, its rapid expansion acts as a relative margin headwind. Consequently, as cloud infrastructure spending ramps up, Amazon offers a much more favorable earnings leverage profile for long-term investors.