Ask HN: Steeper learning curve for back end using phonegap. Rails or Node.js?

I am about to start learning either rails or node.js (express) for back-end development. The plan is once I have learned, down the line I would like to make my web-app also be on mobile. I don't foresee myself learning the native languages for iOS and Android so the plan is to use phonegap.

For rails vs node.js , if I already have a back-end built for a web-app would one or the other be better/easier/more suited to link up to phonegap? Or would it be more or less the same? (just individual preference for which one to use) Thanks!