Recent advancements in large language models (LLMs) have significantly enhanced sentiment analysis capabilities. However, the trade-offs between model performance, efficiency, and explainability of some latest models remain underexplored. This study presents the first comprehensive evaluation of the DeepSeek-R1 series of models, reasoning open-source LLMs, for sentiment analysis, comparing them against OpenAI's GPT-4 and GPT-4-mini. We systematically analyze their performance under few-shot prompting conditions, scaling up to 50-shot configurations to assess in-context learning effectiveness. Our experiments reveal that DeepSeek-R1 demonstrates competitive accuracy, particularly in multi-class sentiment tasks, while offering enhanced interpretability through its detailed reasoning process. Additionally, we highlight the impact of increasing few-shot examples on model performance and discuss key trade-offs between explainability and computational efficiency.