Haven't you heard? Performance doesn't matter; it's all about scalability these days. After all, what's the difference between 100 servers and 200 servers?
Let me get this straight. So you would choose the framework with slightly better plugin support and larger community even if it meant it was three times slower and consumed twice as much memory? If you have deep pockets and have no adversion to unnecessarily managing huge server farms, then go ahead.
I've presided over two rails websites in the past and topping out at around 15req/s on average was not fun. Rewriting to Django and getting 45req/s and less memory usage was definitely worth it. (I'd rate my development experience in other areas to be about equal)