Care to publish if you have anything stored away from this?
I don't work with Rails anymore but the last Rails app(single threaded, Unicorn) I worked with raw CPU compute was not the bottleneck usually as with most CRUD apps time was mostly spent in I/O. This effect was so pronounced that I had set up most scaling groups on M or R instances as the memory used by the gems was the bottleneck on the number of Rails processes I could spawn in the box without exhausting resources. However I do remember even if CPU was not the bottleneck, moving to a processor with a better single thread performance did improve the median response time at the cost of making the same request throughput costlier.
I don't work with Rails anymore but the last Rails app(single threaded, Unicorn) I worked with raw CPU compute was not the bottleneck usually as with most CRUD apps time was mostly spent in I/O. This effect was so pronounced that I had set up most scaling groups on M or R instances as the memory used by the gems was the bottleneck on the number of Rails processes I could spawn in the box without exhausting resources. However I do remember even if CPU was not the bottleneck, moving to a processor with a better single thread performance did improve the median response time at the cost of making the same request throughput costlier.