The question, as you formulated it, is practically impossible to answer with enough certainty to be useful. The difficulty lies in the fact that the problem has many specific factors, such as your personal and professional goals, family situation, mental toughness (perseverance) and others, and only you are aware of them. Thus, only you can figure this out or, rather, try. Therefore, I will address how I believe you could think about the problem, which is essentially common sense.
I think that, basically, you have two options, which, per your question, you seem to understand: 1) easier route, where you choose your research subject and/or topic, based on some arbitrary criteria (for example, based on research interests of a faculty member, which you would like to work with), but avoiding the tough ones; 2) more difficult route, where you choose your research subject and/or topic, based on essential criteria, such as your interests, even if the chosen subject/topic is challenging for you at the moment. In the latter case, you would make commitment to master the subject, despite obstacles, in other words, pushing yourself beyond your current limits. Based on such logical framework, the choice is always yours, and remember that you always have the freedom to re-evaluate your decisions at any moment, should changed circumstances, interests or needs warrant that. Best wishes for whatever route you decide on.