Transfer project from one application to another As a beginner, I would like to know how important it is which software I decide to start out with. (Currently eyeing Adobe Premiere Elements and Sony Movie Studio 13).

I realize that whichever one I'll use, if I decide to switch application, I'll need to learn the other's interface and terminology. However, I was wondering about something else - Can I transfer a project from one to the other. Say I want to make a change to a video I created in one application, and obviously I don't want to input the created video (both because I lose resolution, and because I want each sound track separate etc.) - is it possible to transfer the video to other video editors, or will this project be "stuck" to this editor?
There are ways to transfer projects between different video editing programs, but they are very limited. Take a look at my answer here; this question is about transfering projects between different versions of Premiere Pro, but the answer is basically the same. You can export a project as an Edit Decision List (EDL), however this will only contain the arrangement of the clips in the timeline (namely your edit decisions, hence the name), any effects, e.g. color-grading, will be lost. Another format that does basically the same is AAF. I'm not sure about the differences between both formats, but either way, most of your post-production efforts will be lost when transfering the project to a different program.

Also, this applies to prosumer-/production-level software. I'm not sure whether "low-end" software supports importing and exporting EDL-files. If I remember correctly, it's not possible with Premiere Elements; don't know about the Sony programs (you should be able to find that out over the developer's websites and/or Google).