Energy efficiency has been a daunting challenge for datacenters. The financial industry operates some of the largest datacenters in the world. With increasing energy costs and the financial services sector growth, emerging financial analytics workloads may incur extremely high operational costs, to meet their latency targets. Microservers have recently emerged as an alternative to high-end servers, promising scalable performance and low energy consumption in datacenters via scale-out. Unfortunately, stark differences in architectural features, form factor and design considerations make a fair comparison between servers and microservers exceptionally challenging. In this paper we present a rigorous methodology and new metrics for fair comparison of server and microserver platforms. We deploy our methodology and metrics to compare a microserver with ARM cores against two servers with x86 cores, running the same real-time financial analytics workload. We define workload-specific but platform-independent performance metrics for platform comparison, targeting both datacenter operators and end users. Our methodology establishes that a server based the Xeon Phi processor delivers the highest performance and energy-efficiency. However, by scaling out energy-efficient microservers, we achieve competitive or better energy-efficiency than a power-equivalent server with two Sandy Bridge sockets despite the microserver's slower cores. Using a new iso-QoS (iso-Quality of Service) metric, we find that the ARM microserver scales enough to meet market throughput demand, i.e. a 100% QoS in terms of timely option pricing, with as little as 55% of the energy consumed by the Sandy Bridge server.