Not familiar with RHomobile, but here's what I can tell you after years of working with Appcelerator, Native and Xamarin (xamarin for only a few months)
To me, hands-down, the winner is Appcelerator.
Xamarin appeals to the C# developer in me but, even with the addition of Xamarin Forms in 3.0, there is still too much platform-specific development which will drastically drive up costs.
Compare to Appcelerator, written in JavaScript, where roughly 95% of your code will be shared across all platforms while still providing near-native performance, you just can't compare
With both, you will have to learn the paradigms of native mobile layouts which, if you're a web developer, will be a sizeable undertaking
Web leaks: This is the big myth about Appcelerator which I think is directly linked to the low entry point of JavaScript development. Bottom line, you can write leaky code in any platform. In most cases, Garbage Collection will handle it for you, but if you leave global references scattered throughout your application, you will pay the price, in any platform
As for leaks in the platform itself, Appcelerator did have a few reported, but their platform has matured significantly
Compiles to native: Another myth. Appcelerator is a JavaScript runtime with a bridge-to-native approach; this allows you to use all the features of the JavaScript language; if you are a good JavaScript developer, this is something that will have a significant appeal to you
Maintainability: This is what I love most about any mobile MVC framework vs native. With Appcelerator's MVC app architecture, I find myself adding windows, custom controls, features etc a lot quicker than in Native or Xamarin
Another consideration is that test cycles are very costly in any platform. The ability to test your code in JSFiddle, Codepen, etc, is priceless to me
Hardware support: I've complained about this in the past with Appcelerator. When a new OS feature is released, the bridge-to-native approach will require them to scatter to get the new features built into their bridge; this in turn creates delays in new hardware feature support. If you're comfortable with native development, and you really need the latest and greatest hardware support, you can build the bridge yourself... the process is quite simple
Community: This is what I love most about Appcelerator. You won't find many Appcelerator issues on Stack Overflow because they have their own dev forums and you typically get a question answered within minutes. I'm still waiting for a fairly simple question I asked months ago on Xamarin to be answered; this is one reservation I might have about newer platforms
Documentation: Check out each platform and judge for yourself
Adoption: How likely are you to find talent for a particular technology and how easy will the skillset will translate as you move along in your career
In the end, all these might matter little. The cross-platform mobile landscape is evolving so quickly that I encourage you to pick up many platforms, constantly, as the winners of today may very well be the legacies of tomorrow... Heck if, as programmers, we don't know that already