I expect there will be any number of answers that focus on the technical skillset required to play a piece. I don't think these are incorrect, just perhaps incomplete. The piano instructor I had as a child used to make a joke about using purely technical yardsticks to judge complexity/difficulty of a piece: you can tell how hard it is by how much ink is on the page. The implication being that more notation implied more (technical) difficulty.
I challenged her on that being a joke, under the presumption that technical difficulty was the only difficulty that mattered when evaluating a piece. She proved her point by having me learn some deceptively complex songs I'd never heard before, and then comparing my interpretation of them to typical professional recordings of them.
This brought me to appreciate a more subtle form of difficulty, and eventually realizing a profound truth: music isn't simply the execution of a technical skill. It's an emotionally driving art form.
So: Yes, you should consider technical difficulty when choosing whether to play a piece. Try sight reading it. Consider if it uses notation, scales, etc. you have not yet mastered.
But then, listen to the piece with your "piano ears" turned off. Don't think about how hard it will be to play the right notes at the right tempo. Instead, listen to the emotions the musician is imparting as they interpret the piece. Consider the challenge in imparting your interpretation of the piece in a way that will convey emotion to the audience (even if that audience is just yourself).
I think you hinted at this when you said,
??Enthusiasm towards piece??: a lot
You're likely enthusiastic because the piece gives you an emotional response. That's a great sign - so, now, besides just considering the technical difficulty, make sure you consider the emotional or interpretive difficulty. After all, you want your presentation of the piece to also convey emotion - not just be a simple technical exercise, right?