I hope this is the right place to post this question.

I'm doing my thesis based upon the data of my professors research study. I want to look into wether 2 different psychological treatment conditions affects depression compared to a control group, how they differ, and wether former treatment and medication can predict the outcome (probably through logistic regression).

Frequency analysis of all 3 groups shows that only 25% had been cured. However, analyzing only the two active groups cured 38 individuals 27.1% which gives me a "better" result but a smaller sample size.

Any ideas on which path I should choose? Of course I want a better result, but it feels somewhat wrong to go for the smaller sample size. What would you do?