Bigger sample size and less good results or smaller sample size but better results

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 affect social phobia compared to a control group, how they differ, and wether former treatment, medication and ways of recruitment (newspaper, facebook etc) can predict the outcome (probably through logistic regression).

Frequency analysis of all 3 groups (n=209) shows that only 45 (21.5%) had been cured (that is, had a reduction of 50% on a social phobia measurement scale). However, analyzing only the two active groups (n=140) 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?