OpenAI GPT
Offers powerful language models via API but is proprietary and subscription-based, unlike the open-source Transformers library.
spaCy
Focuses on industrial-strength NLP pipelines with fast inference but has fewer transformer models and less flexibility for fine-tuning.
AllenNLP
Research-focused NLP framework with strong support for custom model development, but smaller model hub compared to Hugging Face.
Fairseq
Facebook AI's sequence modeling toolkit with competitive transformer implementations, but less user-friendly and smaller community.