It depends on what your bottleneck is. RAM? Processor? Bandwidth? If it is RAM, you'd be better off getting fewer servers with more RAM on each. If it is CPU

It depends on what your bottleneck is. RAM? Processor? Bandwidth? If it is RAM, you'd be better off getting fewer servers with more RAM on each. If it is CPU, you'd be better off trying some software configuration options before scaling horizontally. If it is bandwidth, you'd be better off getting a server with a fatter pipe.