You fortunately can try both as both nowadays are completely free to use (while the Unity Free version has a watermark afaik). That's why I'd give both of them a try...

I did and while I liked UE4 more at first (it feels more powerful and developing some advanced C++ skills always is nice). With Unity 5 Free now having access to all features I'm sort of thinking of going back to Unity as I didn't start with anything serious yet. For me the marketplace is a very nice thing to have as it has become quite extensive over the years. As I also would work as a lone wolf it would save me lots of time using e.g. premade particle effects...