The grammar point V+더 is quite versatile and appears in several common forms, each slightly different in nuance:
더라: Expresses spontaneous recall or realization about something you personally witnessed. It's informal and conversational; used when you share immediate thoughts or a reactions.
더라고요: Adds a reflective or explanatory nuance, suggesting you are sharing your observation thoughtfully.
더군요: Conveys a sense of mild surprise and realization — or admiration about what you've experienced. It often feels more emotional or expressive compared to 더라 and 더라고요.