One way to approach this, somewhat ironically, is to show the ways in which Dr. Jekyll and The Monster inFrankensteinattempt to improve themselves. Jekyll initially wants to uncover, understand, and possibly eliminate his repressed "disposition." He even laments the fact that he didn't go about this experiment with more noble, virtuous intent. By physically altering his body, he actually unleashes what he calls his evil side of his dual nature. Had Jekyll gone about it with more virtuous intent, Hyde may have resulted in a moral creature. So, here we have a doctor, an educated man who really turns himself into a kind of crazed drug addict (addicted to malice) all beginning with a veiled attempt at self-improvement.
The Monster actually tries to educate himself. Most notable is his reading of John Milton'sParadise Lost. First, the Monster compares himself with Adam, then he identifies with Satan, a fallen angel. The Monster concludes that, somewhat like Satan, his society rejected him through no fault of his own.
The Monster becomes more human (or humane) while the educated doctor becomes less human (and less humane). The Monster evolves and Jekyll devolves. Dr. Jekyll was trying to understand the evil side of his dual nature and Dr. Frankenstein was trying to understand the nature of life. But if you want a "grabber" using the comparison of these two stories, you could go with a discussion of The Monster as the sympathetic hero who seeks the loving side of human nature while Dr. Frankenstein and Dr. Jekyll only succeed in revealing the evil side. (Dr. Frankenstein immediately disowns The Monster when he is displeased with its result.)