I did some research but couldn't really pin-point and couldn't really come to a conclusion on which one to use and why? Would appreciate some helpful links and differences that can help me reach on a conclusion.
Ionic uses web-based technology. You're basically building a website in a native wrapper. You're still building the app in html/css/js and it will be shipped as such. You might have access to a couple of the native functionalities but that doesn't make an Ionic app a native one.
Titanium is a hybrid technology. You write your code in javascript. Through a layer this javascript talks to native components. So if you make a "Window" in javascript it natively is translated to a window object in Android/iOS. It then also behaves completely native because it actually is. It is as performant as native, as it is native. You just control it with javascript in the background. A well made Titanium app is indistinguishable from a truly native app.
In core, thats the difference.