If you're just delivering content, not number crunching, I doubt your bottlenecks are CPU, and you shouldn't see Erlang take 10x as long. In fact, you'll probably deliver a better experience in Erlang, because of its approach to concurrency; your average latency will likely be a bit higher, but your extremes will likely be lower.
In fact, since you started with benchmarks, let's return to benchmarks (I find them to generally be useless, but you're looking at them, so why not) - http://www.techempower.com/benchmarks/
Compare CPPSP (the fastest! C++!) with cowboy (a popular web framework in Erlang). They're being run on the same hardware (so we're not talking about ability to scale across nodes even), serializing JSON.
Cowboy is about 1/4th the throughput (requests per second). Now let's look at latency. Cowboy took about 4 times the time, .8 ms on average per request to the CPPSP's .2. Great, C++ all the way, right? Err...no. Look at the max and standard deviations.
Cowboy had a max latency of 3.7 ms. CPPSP had a max of 134.6. Standard deviation of cowboy was .3 ms. Standard deviation of CPPSP was .5 ms.
So Cowboy is still really quite fast, more predictable, and has far smaller outliers. What are people going to be more likely to object to, waiting 3.7 ms, or 134 ms?
Couple that with the reliability Erlang provides, the ability to scale straight outta the box (so if you find you're hitting a throughput issue you have a clear path forward), and the joy of functional coding...and it's pretty compelling, to me at least.
This, times a million. 99th percentiles and standard deviation are what truly matters in benchmarks. To liken benchmarks to automobiles, requests/second is horse power and 99th percentile/standard deviation are torque.
In fact, since you started with benchmarks, let's return to benchmarks (I find them to generally be useless, but you're looking at them, so why not) - http://www.techempower.com/benchmarks/
Compare CPPSP (the fastest! C++!) with cowboy (a popular web framework in Erlang). They're being run on the same hardware (so we're not talking about ability to scale across nodes even), serializing JSON.
Cowboy is about 1/4th the throughput (requests per second). Now let's look at latency. Cowboy took about 4 times the time, .8 ms on average per request to the CPPSP's .2. Great, C++ all the way, right? Err...no. Look at the max and standard deviations.
Cowboy had a max latency of 3.7 ms. CPPSP had a max of 134.6. Standard deviation of cowboy was .3 ms. Standard deviation of CPPSP was .5 ms.
So Cowboy is still really quite fast, more predictable, and has far smaller outliers. What are people going to be more likely to object to, waiting 3.7 ms, or 134 ms?
Couple that with the reliability Erlang provides, the ability to scale straight outta the box (so if you find you're hitting a throughput issue you have a clear path forward), and the joy of functional coding...and it's pretty compelling, to me at least.