Extract key phrases for binary outcome
There are a variety of techniques that you could use, depending on what you would like to do.
If your goal is to gain insight into the phrases that are being used in each group, then I'd recommend looking for the most frequent N-grams of different lengths that appear in each class. Here is a related stackoverflow question that shows how you can use nltk and sklearn to extract these.
If your goal is to predict the outcome (accept/reject) given a phrase, then I'd recommend setting this up as a binary classification problem. Since those phrases are quite short, you could start with a Bag of Words approach - the scikit-learn documentation for working with text data is a good example that guides you through the steps.