Paypal developed the Node and Java code in parallel.
"Our first adopter of node.js in production wasn’t a minor application; it was our account overview page and one of the most trafficked apps on the website. We decided to go big, but we also mitigated that risk by building the equivalent Java application in parallel." -- https://www.paypal-engineering.com/2013/11/22/node-js-at-pay...
So, in this case Node wasn't being compared to a legacy system.
"Our first adopter of node.js in production wasn’t a minor application; it was our account overview page and one of the most trafficked apps on the website. We decided to go big, but we also mitigated that risk by building the equivalent Java application in parallel." -- https://www.paypal-engineering.com/2013/11/22/node-js-at-pay...
So, in this case Node wasn't being compared to a legacy system.